Composite electrolyte, protective film including composite electrolyte, protected negative electrode including the protective film, and lithium metal battery including the protected negative electrode

ABSTRACT

A composite electrolyte includes: a positively charged particle, a particle that is positively charged by having a coordinate bond with a cation, or a combination thereof; and a lithium salt.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2017-0170448, filed on Dec. 12, 2017, in the KoreanIntellectual Property Office, and all the benefits accruing therefromunder 35 U.S.C. § 119, the content of which is incorporated herein byreference in its entirety.

BACKGROUND 1. Field

The present disclosure relates to a composite electrolyte, a protectivefilm including the composite electrolyte, a protected negative electrodeincluding the protective film, and a lithium metal battery including theprotected negative electrode.

2. Description of the Related Art

A lithium secondary battery may have excellent charge/dischargeefficiency and capacity, no memory effect, and minimal self-dischargewhen not in use. Thus, since their commercialization, the lithiumsecondary battery has been used as the core electrical component ofportable electronic devices. In recent years, the use of lithiumsecondary batteries has expanded from devices using a small-to-mediumsize battery, such as vacuum machines or power tools, to devices using amedium-to-large size battery, such as electric vehicles, energy storagedevices, and various types of robots.

A lithium secondary battery including a carbonaceous negative electrodematerial has a low energy density and a low discharge capacity. In thisregard, attempts have been made to improve the energy density and thecapacity of the negative electrode for a lithium secondary battery.

In a lithium secondary battery, when lithium metal is used as a negativeelectrode, specific energy, i.e., energy per unit weight, and an energydensity, i.e., energy per unit volume, of the lithium secondary batterymay increase to 3 times relative to non-lithium batteries due to the lowdensity and low oxidation/reduction potential (−3.045 V vs. standardhydrogen electrode (SHE)) of lithium.

Upon electrochemical deposition/stripping of lithium metal, which occursduring charge/discharge processes, there is an increase in the specificsurface area of a negative electrode due to lithium dendrite growth.There is also a side reaction which occurs between lithium metal and anelectrolyte solution and/or anions of the electrolyte solution.Accordingly, the charge and discharge characteristics of lithiumsecondary batteries are poor.

Therefore, it would be desirable to have a lithium secondary batteryhaving improved energy density with improved charge and dischargecharacteristics.

SUMMARY

Provided is a composite electrolyte having increased lithium ionmobility.

Provided is a protective film that may prevent a side reaction between alithium metal negative electrode and an electrolyte solution and/oranions of the electrolyte solution, by including the compositeelectrolyte.

Provided is a protected negative electrode including the protectivefilm, and having suppressed volumetric change upon charging anddischarging.

Provided is a lithium metal battery including the protected negativeelectrode and having improved cycle characteristics.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of an embodiment, a composite electrolyteincludes: a positively charged particle, a particle that is positivelycharged by having a coordinate bond with a cation, or a combinationthereof; and a lithium salt.

According to an aspect of another embodiment, a protective film includesthe composite electrolyte.

According to an aspect of still another embodiment, a protected negativeelectrode includes: a negative electrode including lithium metal or alithium metal alloy; and the protective film on the negative electrode.

According to an aspect of still another embodiment, a lithium batteryincludes: a positive electrode; a protected negative electrode includinglithium metal or a lithium metal alloy, and a protective film on thelithium metal or lithium metal alloy; and an electrolyte between thepositive electrode and the protected negative electrode, wherein theprotective film comprises a composite electrolyte including a positivelycharged particle, a particle that is positively charged by having acoordinate bond with an cation, or a combination thereof; and a lithiumsalt.

According to an aspect of another embodiment, a method of manufacturinga protected negative electrode includes: providing a negative electrodeincluding lithium metal or a lithium metal alloy; and contacting thenegative electrode with a composite electrolyte comprising a positivelycharged particle having a coordinate bond to an cation, and a lithiumsalt to form a protective film on the negative electrode and manufacturethe protected negative electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic view illustrating an embodiment of a positivelycharged particle;

FIG. 2 is a schematic view illustrating an embodiment of a particleincluding a core and a positively charged functional group bound to thecore;

FIG. 3A is a schematic view illustrating an embodiment of a structure inwhich a an ethyldiethylammonium group is bound to a microspherical core;

FIG. 3B is a schematic view illustrating an embodiment in which an anionof a lithium salt is confined to the vicinity of a positively chargedparticle;

FIGS. 4A to 4D are each a schematic view illustrating an embodiment of astructure of a protected negative electrode;

FIGS. 4E and 4F are each a schematic view illustrating a workingprinciple for the suppression and guiding of lithium dendrite growth inan embodiment of a protective film on a negative electrode of a lithiumbattery;

FIGS. 4G to 4I are each a schematic view illustrating an embodiment of astructure of a protected negative electrode;

FIGS. 5A to 5G are each a schematic view illustrating a structure ofvarious embodiments of a lithium battery; and

FIG. 6 is a schematic view illustrating an embodiment of a lithiumbattery.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and should not be construed asbeing limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “At least one” is not to be construed as limiting “a” or“an.” “Or” means “and/or.” As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.Expressions such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items.

As the present inventive concept allows for various changes and numerousembodiments, particular embodiments will be illustrated in the drawingsand described in detail in the written description. However, this is notintended to limit the present inventive concept to particular modes ofpractice, and it is to be appreciated that all changes, equivalents, andsubstitutes that do not depart from the spirit and technical scope ofthe present inventive concept are encompassed in the present inventiveconcept.

The terms used in the present specification are merely used to describeparticular embodiments, and are not intended to limit the presentinventive concept. An expression used in the singular encompasses theexpression of the plural, unless it has a clearly different meaning inthe context. In the present specification, it is to be understood thatthe terms such as “comprises” and/or “comprising,” or “includes” and/or“including”, “having,” or the like, are intended to indicate theexistence of the features, numbers, steps, actions, components, parts,ingredients, materials, or combinations thereof disclosed in thespecification, and are not intended to preclude the possibility that oneor more other features, numbers, steps, actions, components, parts,ingredients, materials, or combinations thereof may exist or may beadded. As used herein, “/” may be construed, depending on the context,as referring to “and” or “or”.

In the drawings, the thicknesses of components, layers and regions areexaggerated or reduced for clarity. Like reference numerals in thedrawings and specification denote like elements. In the presentspecification, it will be understood that when an element, e.g., alayer, a film, a region, or a substrate, is referred to as being “on” or“above” another element, it can be directly on the other element orintervening layers may also be present. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present. While such terms as “first,” “second,” orthe like, may be used to describe various components, such componentsmust not be limited to the above terms. The above terms are used only todistinguish one component from another. In the drawings, some of thecomponents may be omitted to facilitate understanding of the features ofthe present inventive concept, but the present inventive concept is notintended to exclude the omitted components.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10% or 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may have rough and/or nonlinear features. Moreover, sharp anglesthat are illustrated may be rounded. Thus, the regions illustrated inthe figures are schematic in nature and their shapes are not intended toillustrate the precise shape of a region and are not intended to limitthe scope of the present claims.

Hereinafter, according to example embodiments, a composite electrolyte,a protective film, a protected negative electrode, and a lithium metalbattery including the composite electrolyte, the protective film, andthe protected negative electrode are be described in further detail.

As used herein, the term “size” as used in reference to a particle, oralternatively, the term “particle size” may refer to an average particlediameter when the particle has a spherical shape. When the particle hasa rod shape or an elliptical shape, the term “size” or “particle size”may refer to the length along a major axis.

The term “average particle size” or “average particle diameter”, or “D50particle size,” as used herein, refers to a particle diametercorresponding to 50 percent (%) of the particles in a distribution curvein which the particles are accumulated in the order of particle diameterfrom the smallest particle to the largest particle, where the totalnumber of accumulated particles is 100%. The average particle size maybe measured by any suitable method. For example, the average particlesize may be measured with a particle size analyzer, an image from atransmission electron microscope (TEM) or an image from a scanningelectron microscope (SEM). As an example of another type of measuringmethod, the average particle size may be measured with a device usingdynamic light scattering. According to this method, the number ofparticles within a predetermined size range may be counted, and anaverage particle diameter may be calculated therefrom.

The term “porosity” as used herein refers to a measure of the emptyspace (i.e., voids or pores) in a material, which is determined as apercentage of the volume of voids in a material based on the totalvolume of the material.

According to an example embodiment, a composite electrolyte includes apositively charged particle, a particle that is positively charged byhaving a coordinate bond with a cation, or a combination thereof; and alithium salt. Since the composite electrolyte includes a positivelycharged particle and/or a particle that is positively charged by havinga coordinate bond with an cation, i.e., an anion-accepting particle oran anion-withdrawing particle, an anion in the composite electrolyte maybe localized to a surface of and/or in the vicinity of the particle.While not wanting to be bound by theory, it is understood thatlocalizing the anion to a surface of the particle suppresses migrationof anions in the composite electrolyte. The suppressed anion migrationis understood to result in increased lithium ion migration in thecomposite electrolyte, resulting in an increase in the lithium iontransference number in the composite electrolyte.

Referring to FIG. 1 , to maintain electrical neutrality, an anion 101may be present on a surface of and/or in the vicinity of a positivelycharged particle 100. The particle that is positively charged by havinga coordinate bond with a cation may be electrically neutral when theparticle is not coordinated with a cation (e.g., a functional grouprepresented by Formula 2); however, when unshared electrons areincluded, the particle may become the positively charged particle 100through a coordinate bond, e.g. coordinate covalent bond, with a cation,e.g., proton. The particle that is positively charged by a coordinatebond with a cation may be present substantially as the positivelycharged particle 100 in the composite electrolyte including a lithiumsalt.

Referring to FIG. 2 , the positively charged particle 100 includes acore 102 and a plurality of positively charged functional groups 103bound to the core 102. Accordingly, a plurality of anions 101 may bepresent in the vicinity of the positively charged particle 100. Each ofthe plurality of positively charged functional groups 103 may be boundto the core 102 via a covalent bond. The particle that is positivelycharged by a coordinate bond with a cation, may include a core and afunctional group that is positively charged by a coordinate bond with acation and which is bound to the surface of the core. For example, atertiary amine group may change to a quaternary ammonium cation group bya coordinate bond with a proton. Thus, a functional group capable ofbeing positively charged by a coordinate bond with a cation changes intoa positively charged functional group by a coordinate bond with aproton. The functional group having a coordinate bond with a cation hasa positive charge and thus may also be referred to herein as afunctional group positively charged by a coordinate bond with a cation.

Hereinafter, unless otherwise indicated, a “particle” refers to apositively charged particle and/or a particle positively charged by acoordinate bond with an ion.

A monomeric compound providing the functional group that is positivelycharged by a coordinate bond with a cation may be a weak base, wherein apKa value of a conjugate acid of the monomeric compound may be 12 orlower, 11.5 or lower, 11 or lower, or 10.5 or lower. For example, a pKavalue of a conjugated acid of the monomeric compound may be in a rangeof about 5 to about 12, about 5 to about 11.5, about 6 to about 11, orabout 7 to about 10.5. The monomeric compound providing the functionalgroup that is positively charged by a coordinate bond with a cationrefers to a monomeric compound substituted with a hydrogen atom. Thecore may be bound to the functional group that may be positively chargedby a coordinate bond with a cation. For example, as shown in FIG. 3A, ina particle in which a dimethyl ethyl amine group (—CH₂CH₂N(CH₃)₂) isbound to the core 102, the monomeric compound providing the dimethylethyl amine group may be dimethyl ethyl amine, and a pKa value of aconjugated acid of the dimethyl ethyl amine may be 10.16.

The positively charged functional group may be represented by Formula 1,and the functional group that is positively charged by a coordinate bondwith a cation may be represented by Formula 2:

wherein, in Formulae 1 and 2,

X may be O, S, or a covalent bond, Y may be N or P, Z may be N or B, R₁,R₂, R₃, R₅, and R₆ may each independently be hydrogen, a C₁-C₂₀ alkylgroup that is unsubstituted or substituted with a halogen, a C₂-C₂₀alkenyl group that is unsubstituted or substituted with a halogen, aC₂-C₂₀ alkynyl group that is unsubstituted or substituted with ahalogen, a C₅-C₂₀ aryl group that is unsubstituted or substituted with ahalogen, or a C₂-C₂₀ heteroaryl group that is unsubstituted orsubstituted with a halogen, and R₄ and R₇ may each independently be aC₁-C₂₀ alkylene group that is unsubstituted or substituted with ahalogen.

In some embodiments, the positively charged functional group may berepresented by Formulae 3 to 10, or a combination thereof:

In some embodiments, the functional group positively charged by acoordinate bond with a cation may be represented by Formulae 11 to 18,or a combination thereof:

Referring to FIG. 2 , an anion that confined to the vicinity of thepositively charged particle may be any suitable anion. The anion may be,for example, separated from a lithium salt, which is divided into ananion and a lithium cation. The anion may be, for example, BF⁴⁻, PF⁶⁻,AsF⁶⁻, SbF⁶⁻, AlCl⁴⁻, HSO⁴⁻, ClO⁴⁻, CH₃SO³⁻, CF₃CO²⁻, Cl⁻, Br⁻, I⁻, SO₄²⁻, CF₃SO₃ ⁻, (FSO₂)₂N⁻, (C₂F₅SO₂)₂N⁻, (C₂F₅SO₂)(CF₃SO₂)N⁻, (CF₃SO₂)₂N⁻,or a combination thereof.

Referring to FIG. 3A, the positively charged particle 100 may include acore 102 which is microspherical and a functional group 103 bound to thesurface of the core. The functional group 103 may include adiethylaminoethyl group coordinated with a proton.

Referring to FIG. 3B, the positively charged particle 100 may includethe core 102 and the positively charged functional group 103 bound tothe core 102. An anion 101 (e.g., bis(fluoro sulfonyl)imide anion, FSI⁻)derived from a lithium salt may be confined to the vicinity of thepositively charged functional group 103.

The particle may include an organic particle, an inorganic particle, anorganic-inorganic particle, or a combination thereof. The organicparticle may include an organic core. The inorganic particle may includean inorganic core. The organic-inorganic particle may include anorganic-inorganic core.

The organic particle of the composite electrolyte may include apolystyrene homopolymer, a copolymer including a styrene repeating unit,polymethyl methacrylate, a copolymer containing a repeating unit havinga crosslinkable functional group, a crosslinked polymer thereof, or acombination thereof.

The inorganic particle and the organic-inorganic particle of thecomposite electrolyte may include silica, titania, alumina, BaTiO₃, acage-structured silsesquioxane, a metal-organic framework (MOF),Li_(1+x+y)Al_(x)Ti_(2−x)Si_(y)P_(3−y)O₁₂, wherein 0<x<2 and 0≤y<3,BaTiO₃, Pb(Zr_(x)Ti_(1-x))O₃ wherein 0≤x<1 (PZT),Pb_(1-x)La_(x)Zr_(1-y)Ti_(y)O₃ (PLZT), wherein 0≤x<1 and 0≤y<1,Pb(Mg₃Nb_(2/3))O₃—PbTiO₃ (PMN-PT), HfO₂, SrTiO₃, SnO₂, CeO₂, Na₂O, MgO,NiO, CaO, BaO, ZnO, ZrO₂, Y₂O₃, Al₂O₃, TiO₂, SiO₂, SiC, lithiumphosphate (Li₃PO₄), lithium titanium phosphate (Li_(x)Ti_(y)(PO₄)₃),wherein 0<x<2 and 0<y<3, lithium aluminum titanium phosphate(Li_(x)Al_(y)Ti_(z)(PO₄)₃, wherein 0<x<2, 0<y<1, and 0<z<3,Li_(1+x+y)(Al, Ga)_(x)(Ti, Ge)_(2−x)Si_(y)P_(3−y)O₁₂, wherein 0≤x≤1 and0≤y≤1, lithium lanthanum titanate (Li_(x)La_(y)TiO₃), wherein 0<x<2 and0<y<3, lithium germanium thiophosphate (Li_(x)Ge_(y)P_(z)S_(w)), wherein0<x<4, 0<y<1, 0<z<1, and 0<w<5, lithium nitride (Li_(x)N_(y)), wherein0<x<4 and 0<y<2, a SiS₂-type glass (Li_(x)Si_(y)S_(z)), wherein 0<x<3,0<y<2, and 0<z<4, a P₂S₅-type glass (Li_(x)P_(y)S_(z)), wherein 0<x<3,0<y<3, and 0<z<7, Li₂O, LiF, LiOH, Li₂CO₃, LiAlO₂, aLi₂O—Al₂O₃—SiO₂—P₂O₅—TiO₂—GeO₂-based ceramic, a garnet-based ceramic,Li_(3+x)La₃M₂O₁₂, wherein 0≤x≤5 and M=Te, Nb, or Zr; a crosslinkedstructure thereof; or a combination thereof. The inorganic particle mayoptionally further include a crosslinkable functional group and thus aninorganic particle may have a crosslinked structure by the crosslinkablefunctional groups. In addition, when the inorganic particle has acrosslinkable functional group, an organic-inorganic particle comprisingthe organic particle and the inorganic particle may have a crosslinkedstructure.

The organic particle of the composite electrolyte may include anysuitable polymer that may be used in forming a protective film. Theparticle in the protective film may include a polymer having lowwettability against a liquid electrolyte.

The organic particle of the composite electrolyte may include an organicparticle including a polystyrene homopolymer, a copolymer including astyrene repeating unit, a copolymer containing a repeating unit having acrosslinkable functional group, a crosslinked polymer thereof, or acombination thereof.

The organic particle of the composite electrolyte may include a polymerincluding a styrene-based repeating unit (e.g., a styrene homopolymer orcopolymer). When the organic particle is a polymer including astyrene-based repeating unit, which is hydrophobic and essentially notwettable to an electrolyte, the polymer may not adversely affect thelithium metal electrode, and the reactivity of the lithium metalelectrode with the electrolyte may be suppressed.

The organic particle may include a polystyrene homopolymer, apoly(styrene-divinylbenzene) copolymer, a poly(methylmethacrylate-divinylbenzene) copolymer, a poly(ethylmethacrylate-divinylbenzene) copolymer, a poly(pentylmethacrylate-divinylbenzene) copolymer, a poly(butylmethacrylate-divinylbenzene) copolymer, a poly(propylmethacrylate-divinylbenzene) copolymer, a poly(styrene-ethylenebutylene-styrene) copolymer, a poly(styrene-methyl methacrylate)copolymer, a poly(styrene-acrylonitrile) copolymer, apoly(styrene-vinylpyridine) copolymer, apoly(acrylonitrile-butadiene-styrene) copolymer, apoly(acrylonitrile-ethylene-propylene-styrene) copolymer, a poly(m ethylmethacrylate-acrylonitrile-butadiene-styrene) copolymer, apoly(methacrylate-butadiene-styrene) copolymer, a poly(styrene-acrylate)copolymer, a poly(acrylonitrile-styrene-acrylate) copolymer; acrosslinked structure thereof; or a combination thereof. The organicparticle may be, for example, a poly(styrene-vinylbenzene) copolymer.

The polymer may be a crosslinked polymer. The crosslinked polymer may bea poly(styrene-divinylbenzene) copolymer, a poly(methylmethacrylate-divinylbenzene), or combination thereof. When the copolymercontains the styrene-based repeating unit, a content of thestyrene-based repeating unit may be in a range of about 65 parts byweight to about 99 parts by weight, about 80 parts by weight to about 99parts by weight, about 90 parts by weight to about 99 parts by weight,or for example, about 96 parts by weight to about 99 parts by weight,based on 100 parts by weight of the total weight of the copolymer. Whenthe copolymer contains divinylbenzene, a content of the divinylbenzenemay be in a range of about 1 part by weight to about 35 parts by weight,about 1 part by weight to about 20 parts by weight, about 1 part byweight to about 10 parts by weight, or about 1 part by weight to about 4parts by weight, for example, about 3 parts by weight to about 7 partsby weight or about 3 parts by weight to about 5 parts by weight, basedon 100 parts by weight of the total weight of the copolymer. Thecopolymer described above may include a block copolymer, a randomcopolymer, an alternating copolymer, a graft copolymer, or a combinationthereof. A weight average molecular weight of the copolymer may be in arange of about 10,000 Daltons to about 1,000,000 Daltons, about 10,000Daltons to about 500,000 Daltons, about 10,000 Daltons to about 200,000Daltons, or about 15,000 Daltons to about 150,000 Daltons, or about20,000 Daltons to about 150,000 Daltons. The copolymer may be, forexample, a block copolymer.

In sequence, blocks that constitute the copolymer are referred to as ablock including a first repeating unit (a first block), a blockincluding a second repeating unit (a second block), and a blockincluding a third repeating unit (a third block). The first blockincluding the first repeating unit may have a weight average molecularweight of 10,000 Daltons or greater, in a range of about 10,000 Daltonsto about 500,000 Daltons, or for example, about 15,000 Daltons to about400,000 Daltons, or about 20,000 to about 350,000 Daltons. A content ofthe first block including the first repeating unit may be in a range ofabout 20 parts by weight to about 50 parts by weight, or about 20 partsby weight to about 40 parts by weight, or for example, about 22 parts toabout 30 parts by weight, based on 100 parts by weight of the totalweight of the block copolymer. When such a polymer block is used, aprotective film may have good mechanical properties, e.g., improvedstrength. The second block including the second repeating unit may havea weight average molecular weight of 10,000 Daltons or greater, in arange of about 10,000 Daltons to about 500,000 Daltons, or for example,about 15,000 Daltons to about 400,000 Daltons, or about 20,000 Daltonsto about 350,000 Daltons. When such a hard block having a weight averagemolecular weight within any of these ranges is used, the protective filmmay have improved ductility, elasticity, and strength characteristics.

The block copolymer may be at least one selected from a diblockcopolymer (A-B) and a triblock copolymer (A-B-A′ or B-A-B′). In atriblock copolymer including the first block, the second block, and thethird block, a total content of the first block and the third block maybe in a range of about 20 parts by weight to about 35 parts by weight,or for example, about 20 parts by weight to about 33 parts by weight, orabout 22 parts by weight to about 30 parts by weight, and a content ofthe second block may be in a range of about 65 parts to about 80 partsby weight, or about 67 parts by weight to about 79 parts by weight, orfor example about 70 parts to about 78 parts by weight, based on 100parts by weight of the total weight of the block copolymer.

The organic particle of the composite electrolyte may include polyvinylpyridine, polyvinyl cyclohexane, poly glycidyl acrylate,poly(2,6-dimethyl-1,4-phenylene oxide), polyolefin, poly(tertbutyl vinylether), poly(cyclohexyl vinyl ether), polyvinyl fluoride, apoly(styrene-maleic anhydride) copolymer, poly(glycidyl methacrylate),polyacrylonitrile, a polymeric ionic liquid (PIL), or a combinationthereof.

The organic particle of the composite electrolyte may include apoly(styrene-divinylbenzene) copolymer, a poly(methylmethacrylate-divinylbenzene) copolymer, a poly(ethylmethacrylate-divinylbenzene) copolymer, a poly(pentylmethacrylate-divinylbenzene) copolymer, a poly(butylmethacrylate-divinylbenzene) copolymer, a poly(propylmethacrylate-divinylbenzene) copolymer, apoly(methylacrylate-divinylbenzene) copolymer, a poly(ethylacrylate-divinylbenzene) copolymer, a poly(pentylacrylate-divinylbenzene) copolymer, a poly(butylacrylate-divinylbenzene) copolymer, a poly(propylacrylate-divinylbenzene) copolymer, a poly(pentylacrylate-divinylbenzene) copolymer, apoly(acrylonitrile-butadiene-styrene) copolymer, or a combinationthereof.

When the organic particle in the composite electrolyte includes acrosslinked polymer as described above, individual particles may beconnected to each other due to the crosslinking between the particles,and as a result, the composite electrolyte may have improved mechanicalstrength. A degree of crosslinking of the composite electrolyte may bein a range of about 10% to about 30%, or for example, about 12% to about28%, or about 12% to about 25%, based on the total compositeelectrolyte.

An average particle size of the particle in the composite electrolytemay be in a range of about 10 nanometers (nm) to about 100 micrometers(μm), about 20 nm to about 70 μm, about 30 nm to about 50 μm, about 40nm to about 50 μm, about 50 nm to about 50 μm, about 0.1 μm to about 50μm, about 0.3 μm to about 50 μm, about 0.3 μm to about 20 μm, about 0.5μm to about 10 μm, about 1 μm to about 5 μm, or about 1.5 μm to about 5μm. The particle may be a nanoparticle or a microparticle.

The particle included in the composite electrolyte may have a sphericalshape, a microspherical shape, a rod shape, an oval shape, or a radialshape. When the particle has a spherical shape, the particle may be amicrosphere having an average diameter, for example, in a range of about0.1 μm to about 50 μm, about 0.3 μm to about 50 μm, about 0.3 μm toabout 20 μm, about 0.5 μm to about 10 μm, or about 1 μm to about 5 μm.When the particle includes particles having different sizes, theparticles may include a first particle having a large diameter and asecond particle having a small diameter. For example, the particle mayinclude a first particle having a size of about 8 μm as a large diameterparticle and a second particle having a size of about 4 μm as a smalldiameter particle. In some embodiments, the particle may include a firstparticle having a size of about 3 μm as a large diameter particle and asecond particle having a size of about 1.3 μm as a small diameterparticle. A mixed weight ratio of the first (large diameter) particle tothe second (small diameter) particle may be, for example, in a range ofabout 4:1 to about 9:1, or may be about 5:1, or about 6:1, or about 7:1,or about 8:1.

The lithium salt in the composite electrolyte may include, for example,LiSCN, LiN(CN)₂, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, LiC(CF₃SO₂)₃,LiN(SO₂C₂F₅)₂, LiN(SO₂CF₃)₂, LiN(SO₂F)₂, LiSbF₆, LiPF₃(CF₂CF₃)₃,LiPF₃(CF₃)₃, LiB(C₂O₄)₂, or a combination thereof.

The composite electrolyte may be a composite solid electrolyte thatfurther includes a polymer. The polymer in the composite solidelectrolyte may include polyethylene oxide (PEO), polyvinylidenefluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP),a poly(styrene-b-ethyleneoxide) block copolymer (PS-PEO),poly(styrene-butadiene), poly(styrene-isoprene-styrene), apoly(styrene-b-divinylbenzene) block copolymer, apoly(styrene-ethyleneoxide-styrene) block copolymer, or a combinationthereof.

In the composite solid electrolyte, a content of the particle may be ina range of about 5 parts by weight to about 20 parts by weight, or about5 parts by weight to about 18 parts by weight, or about 5 parts byweight to about 15 parts by weight, based on 100 parts by weight of thepolymer. A content of the lithium salt may be in a range of about 5parts by weight to about 40 parts by weight, or about 7 parts by weightto about 35 parts by weight, or about 10 parts by weight to about 30parts by weight, based on 100 parts by weight of the polymer. However,the amounts of the particle and the lithium salt are not particularlylimited thereto, and may be adjusted by the person of ordinary skill inthe art without undue experimentation.

When the composite electrolyte includes the particle including thepositively charged particle, the particle having a coordinate bond witha cation, or the combination thereof, the lithium ion mobility of thecomposite electrolyte may be greater than the lithium ion mobility of acomposite electrolyte without the particle (particle-free compositeelectrolyte), greater than a lithium ion mobility of a compositeelectrolyte including a particle that is not positively charged, or acombination thereof.

According to another example embodiment, a protective film may includethe composite electrolyte.

As the protective film includes the composite electrolyte including thepositively charged particle, the particle having a coordinate bond witha cation, or a combination thereof, a side reaction between a lithiummetal negative electrode and an electrolyte solution and/or anions ofthe electrolyte solution, which are positioned next to the protectivefilm, may be effectively suppressed.

The protective film may have a tensile modulus of 10⁶ pascals (Pa) orgreater, 10⁷ Pa or greater, or 10⁸ Pa or greater. For example, theprotective film has a tensile modulus in a range of about 10⁶ Pa toabout 10¹⁰ Pa, or about 10⁷ Pa to about 10¹⁰ Pa, or about 10⁸ Pa toabout 10¹⁰ Pa, and as a result, the protective film may have excellentmechanical strength as well as elasticity. For example, the protectivefilm may have a greater tensile modulus than lithium metal, and as aresult, volumetric change of the lithium metal may be suppressed, andgrowth of lithium dendrites may be effectively suppressed.

The tensile modulus has the same meaning as Young's modulus. The tensilemodulus may be measured by Dynamic Mechanical Analysis (DMA) using aDMA800 (available from TA Instruments Inc.). Protective film samples forthe tensile modulus measurement may be prepared according to the ASTMstandard D412 (Type V specimens). Variations in strain with respect tostress in the protective film may be measured at a temperature of about25° C., a relative humidity of about 30%, and a rate of 5 millimetersper minute (mm/min). The tensile modulus may be calculated from theslope of a stress-strain curve thereof.

The particle in the protective film may have a chemically or physicallycrosslinked structure. The particle having a chemically or physicallycrosslinked structure may include, for example, an organic particleincluding a crosslinked polymer obtained from a polymer having acrosslinkable functional group, an inorganic particle having acrosslinked structure due to a crosslinkable functional group on asurface thereof, or the like, or may be a combination thereof. Thecrosslinkable functional group, which is involved in a crosslinkingreaction, may be, for example, an acryl group, a methacryl group, avinyl group, or the like.

A particle having a chemically crosslinked structure refers to aparticle in which crosslinking has occurred using chemical methods(e.g., chemical agents) to facilitate the formation of a chemical bondbetween crosslinkable functional groups present in the material forforming the particle. A particle having a physically crosslinkedstructure refers to a particle in which crosslinking has occurred usingphysical methods, for example, by heating a polymer forming the particleuntil it reaches its glass transition (T_(g)) temperature. Thecross-linking may occur within the particle itself, between adjacentparticles in the protective layer, or may be a combination thereof.

The protective film may include a crosslinked product of a polymerizableoligomer between the particles.

The polymerizable oligomer refers to an oligomer having a crosslinkablefunctional group. A weight average molecular weight of the polymerizableoligomer may be 5,000 Daltons or less, for example, 2,000 Daltons orless, 1,000 Daltons or less, in a range of about 200 Daltons to about1,000 Daltons, or about 200 Daltons to about 750 Daltons, or about 200Daltons to about 500 Daltons. When a polymerizable oligomer has a weightaverage molecular weight within any of the above-described ranges, thepolymerizable oligomer may be in a liquid state or in a state thatallows the polymerizable oligomer to be dissolved and easily injectedinto a solvent. Such a polymerizable oligomer may have a low viscositycharacteristics in a range of about 3 centipoise (cP) to about 50 cP, orabout 3 cP to about 30 cP, or about 3 cP to about 20 cP. When acomposition including a polymerizable oligomer having a viscosity withinthe above-described ranges is used, a process of injecting into andfilling a space between particles of a protective film may be easilycarried out, thereby manufacturing a protective film having a highstrength.

A weight average molecular weight of the crosslinked material of thepolymerizable oligomer may be in a range of about 10,000 Daltons toabout 300,000 Daltons, or about 10,000 Daltons to about 300,000 Daltons,or about 15,000 Daltons to about 275,000 Daltons, and a degree ofcrosslinking of the crosslinked material of the polymerizable oligomermay be, for example, 90% or greater, or for example, in a range of about90% to about 100%.

The polymerizable oligomer may include diethylene glycol diacrylate(DEGDA), triethylene glycol diacrylate (TEGDA), tetraethylene glycoldiacrylate (TTEGDA), polyethylene glycol diacrylate (PEGDA), dipropyleneglycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA),ethoxylated trimethylolpropane triacrylate (ETPTA),acrylate-functionalized ethylene oxide, 1,6-hexanediol diacrylate,ethoxylated neopentyl glycol diacrylate (NPEOGDA), propoxylatedneopentyl glycol diacrylate (NPPOGDA), allyl methacrylate (ALMA),trimethylol propane triacrylate (TMPTA), trimethylol propanetrimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA),ethoxylated/propoxylated trimethylolpropane triacrylate(TMPEOTA)/(TMPPOTA), glyceryl propoxylated triacrylate (GPTA)/(GPPOTA),tris(2-hydroxyethyl) isocyanurate triacrylate (THEICTA), pentaerythritoltetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPEPA), or acombination thereof.

The polymerizable oligomer and a crosslinked material of thepolymerizable oligomer prepared therefrom may have ionic conductivity.When a polymerizable oligomer and a crosslinked material of thepolymerizable oligomer have ionic conductivity, the ionic conductivityof the protective film may further improve.

A content of the crosslinked material of the polymerizable oligomer inthe protective film may be in a range of about 10 parts by weight toabout 50 parts by weight, or about 15 parts by weight to about 45 partsby weight, or for example, about 20 parts by weight to about 40 parts byweight, based on 100 parts by weight of the particle. When a content ofthe crosslinked material of the polymerizable oligomer is within any ofthese ranges, the protective film may have excellent mechanicalproperties.

The protective film may include a liquid electrolyte. When theprotective film includes a liquid electrolyte, the liquid electrolytemay form an ion conducting path so that the conductivity of the negativeelectrode may improve. Accordingly, a lithium metal battery having astable cycle characteristics may be obtained. For example, the liquidelectrolyte may be disposed on a protective film in a solid state, andthus the protective film may be impregnated with the liquid electrolyteto thereby obtain a protective film including a liquid electrolyte.

The liquid electrolyte may include an organic solvent, a lithium salt,or a combination thereof. The liquid electrolyte may occupy about 30volume percent (%) to about 60 volume % of the total volume of theprotective film. For example, the liquid electrolyte may occupy 35volume % to about 55 volume %, or about 40 volume % to about 50 volume %of the total volume of the protective film.

The lithium salt included in the protective film may be, for example,LiSCN, LiN(CN)₂, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, LiC(CF₃SO₂)₃,LiN(SO₂C₂F₅)₂, LiN(SO₂CF₃)₂, LiN(SO₂F)₂, LiSbF₆, LiPF₃(CF₂CF₃)₃,LiPF₃(CF₃)₃, LiB(C₂O₄)₂, or a combination thereof. A content of thelithium salt of the protective film may be in a range of about 10 partsby weight to about 70 parts by weight, about 20 parts by weight to about60 parts by weight, or about 20 parts by weight to about 50 parts byweight, based on 100 parts by weight of the particle. When the contentof the lithium salt is within any of these ranges, the protective filmmay have good ion conductivity.

The organic solvent included in the protective film may include acarbonate compound, a glyme compound, a dioxolane compound, or acombination thereof. For example, the carbonate compound may includeethylene carbonate, propylene carbonate, dimethyl carbonate,fluoroethylene carbonate, diethyl carbonate, or ethyl methyl carbonate,or a combination thereof. The glyme compound may include, for example,poly(ethylene glycol)dimethyl ether (PEGDME; polyglyme), tetra(ethyleneglycol)dimethyl ether (TEGDME; tetraglyme), tri(ethylene glycol)dimethylether (triglyme), poly(ethylene glycol)dilaurate (PEGDL), poly(ethyleneglycol)monoacrylate (PEGMA), poly(ethylene glycol)diacrylate (PEGDA), ora combination thereof. The dioxolane compound may include, for example,3-dioxolane, 4,5-diethyl-1,3-dioxolane, 4,5-dimethyl-1,3-dioxolane,4-methyl-1,3-dioxolane, 4-ethyl-1,3-dioxolane, or a combination thereof.Examples of the organic solvent include 2,2-dimethoxy-2-phenylacetophenone, dimethyl ether (DME), 1,2-dimethoxyethane,1,2-diethoxyethane, tetrahydrofuran (THF), γ-butyrolactone,1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, or acombination thereof.

The organic solvent may include ethylene carbonate, propylene carbonate,dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate,fluoroethylene carbonate, γ-butyrolactone, dimethoxyethane,diethoxyethane, diethylene glycol dimethyl ether, triethylene glycoldimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycoldimethyl ether, succinonitrile, sulfolane, dimethyl sulfone, ethylmethyl sulfone, diethyl sulfone, adiponitrile, tetraethylene glycol,1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, or acombination thereof.

The protective film may further include an ionic liquid, a metal saltincluding a Group 1 or 2 element, and a nitrogen-containing additive,boron nitride, an ion conductive polymer, or a combination thereof.

The term “ionic liquid” refers to a salt in a liquid state at roomtemperature or a room temperature molten salt having a melting point ofroom temperature or less and consisting of ions. The ionic liquid may bea compound including: a cation including an ammonium cation, apyrrolidinium cation, a pyridinium cation, a pyrimidinium cation, animidazolium cation, a piperidinium cation, a pyrazolium cation, anoxazolium cation, a pyridazinium cation, a phosphonium cation, asulfonium cation, a triazolium cation, or a combination thereof; and ananion including BF₄ ⁻, PF₆ ⁻AsF₆ ⁻, SbF₆ ⁻, AlCl₄ ⁻, HSO₄ ⁻, ClO₄ ⁻,CH₃SO₃ ⁻, CF₃CO₂ ⁻, Cl⁻, Br⁻, I⁻, SO₄ ²⁻, CF₃SO₃ ⁻, (FSO₂)₂N⁻,(C₂F₅SO₂)₂N⁻, (C₂F₅SO₂)(CF₃SO₂)N⁻, CF₃SO₂)₂N⁻, or a combination thereof.

For example, the ionic liquid may include N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(3-trifluoromethylsulfonyl)imide,1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or acombination thereof.

A content of the ionic liquid in the protective film may be in a rangeof about 5 parts by weight to about 40 parts by weight, or about 10parts by weight to about 30 parts by weight, or about 10 parts by weightto about 20 parts by weight, based on 100 parts by weight of theparticle. When the content of the ionic liquid is within any of theseranges, the protective film may have improved ion conductivity andimproved mechanical properties.

When the protective film includes an ionic liquid and a lithium salt, amole ratio (IL/Li) of the ionic liquid (IL) to lithium ions (Li) may bein a range of about 0.1 to about 2, for example, about 0.2 to about 1.8,or for example, about 0.4 to about 1.5. When the mole ratio of the ionicliquid to lithium ions is within any of these ranges, the protectivefilm may have high lithium ion mobility, high ion conductivity, andimproved mechanical properties to effectively suppress growth of lithiumdendrite on a surface of the negative electrode.

The metal salt including a Group 1 or 2 element may be a metal saltincluding Cs, Rb, K, Ba, Sr, Ca, Na, Mg, or a combination thereof.

The nitrogen-containing additive may include an inorganic nitrate, anorganic nitrate, an inorganic nitrite, an organic nitrite, an organicnitro compound, an organic nitroso compound, a N—O compound, a lithiumnitride (Li₃N), or a combination thereof.

A metal salt containing a Group 1 or 2 element, a nitrogen-containingadditive, or a combination thereof, may be insoluble in an organicsolvent of a liquid electrolyte. Thus, the metal salt containing a Group1 or 2 element and the nitrogen-containing additive may beelectrochemically stable on a surface of a lithium metal negativeelectrode. Mobility of the metal salt containing a Group 1 or 2 elementand the nitrogen-containing additive is limited; thus, lithium ionmobility in a protective film including the metal salt and thenitrogen-containing additive may not be substantially affected. Themetal of the metal salt containing a Group 1 or 2 element has arelatively larger atom size than lithium and thus may have a sterichindrance effect in the protective film. Without being limited bytheory, it is believed that due to this steric hindrance, it may bepossible to suppress growth of lithium dendrites on a surface of thelithium metal negative electrode. A metal cation (for example, cesium(Cs) or rubidium (Rb) ions) in the metal salt containing a Group 1 or 2element may exhibit an effective reduction potential below the reductionpotential of lithium ions and thus may form a positively chargedelectrostatic shield around the initial growth tip of protuberancesformed on a surface of the lithium metal negative electrode, without anyreduction or deposition of the metal salt during lithium deposition. Thepositively charged electrostatic shield may effectively suppress growthof lithium dendrites on a surface of the lithium metal negativeelectrode. In order for the metal salt containing a Group 1 or 2 elementto have an effective reduction potential below the reduction potentialof lithium ions, the content of the metal salt containing a Group 1 or 2element may be in a range of about 0.1 parts by weight to about 100parts by weight, or about 1 part by weight to about 75 parts by weight,or about 10 parts by weight to about 50 parts by weight, based on 100parts by weight of the particle.

The polymeric ionic liquid which may be added to the protectivefilm-forming composition may be, for example, a polymerization productof ionic liquid monomers, or a polymeric compound. The polymeric ionicliquid is highly dissoluble in an organic solvent, and thus may furtherimprove the ion conductivity of a protective film when added to theprotective film-forming composition.

When the polymeric ionic liquid is prepared by polymerization of ionicliquid monomers, a resulting product from the polymerization reactionmay be washed and dried, followed by an anionic substitution reaction tohave appropriate anions that may improve solubility in an organicsolvent.

The polymer ionic liquid may include a repeating unit including: anammonium cation, a pyrrolidinium cation, a pyridinium cation, apyrimidinium cation, an imidazolium cation, a piperidinium cation, apyrazolium cation, an oxazolium cation, a pyridazinium cation, aphosphonium cation, a sulfonium cation, a triazolium cation, or acombination thereof; and BF₄ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, AlCl₄ ⁻, HSO₄ ⁻,ClO₄ ⁻, CH₃SO₃ ⁻, CF₃CO₂ ⁻, (CF3SO2)2N—, (FSO2)2N—, Cl—, Br—, I—, SO4—,CF₃SO₃ ⁻, (C₂F₅SO₂)₂N⁻, (C₂F₅SO₂)(CF₃SO₂)N⁻, NO₃ ⁻, Al₂Cl₇ ⁻,(CF₃SO₂)₃C⁻, (CF₃)₂PF₄ ⁻, (CF₃)₃PF₃ ⁻, (CF₃)₄PF₂ ⁻, (CF₃)₅PF⁻, (CF₃)₆P⁻,SF₅CF₂SO₃ ⁻, SF₅CHFCF₂SO₃ ⁻, CF₃CF₂(CF₃)2CO⁻, CF₃SO₂)₂CH⁻, (SF₅)₃C⁻,(O(CF₃)₂C₂(CF₃)₂O)₂PO⁻, or a combination thereof.

The ionic liquid monomer used in preparing the polymer ionic liquid mayhave a functional group that is polymerizable with a vinyl group, anallyl group, an acrylate group, or a methacrylate group and may have acation including an ammonium cation, a pyrrolidinium cation, apyridinium cation, a pyrimidinium cation, an imidazolium cation, apiperidinium cation, a pyrazolium cation, an oxazolium cation, apyridazinium cation, a phosphonium cation, a sulfonium cation, atriazolium cation, or a combination thereof, and at least one of theabove-listed anions.

Examples of the ionic liquid monomer include 1-vinyl-3-ethylimidazoliumbromide and compounds represented by Formula 19 or 20:

For example, the polymeric ionic liquid may be a compound represented byFormula 21 or a compound represented by Formula 22:

In Formula 21, R₁ and R₃ may each independently be hydrogen, asubstituted or unsubstituted C₁-C₃₀ alkyl group, a substituted orunsubstituted C₂-C₃₀ alkenyl group, a substituted or unsubstitutedC₂-C₃₀ alkynyl group, a substituted or unsubstituted C₆-C₃₀ aryl group,a substituted or unsubstituted C₂-C₃₀ heteroaryl group, a substituted orunsubstituted C₄-C₃₀ carbocyclic group; R₂ may be a single bond, a C₁-C₃alkylene group, a C₆-C₃₀ arylene group, a C₂-C₃₀ heteroarylene group, ora C₄-C₃₉ carbocyclic group; X⁻ may be an anion of an ionic liquid; and nmay be in a range of about 500 to about 2,800.

In Formula 22, Y⁻ is defined the same as X⁻ in Formula 21, and n may bein a range of about 500 to about 2,800.

In Formula 22, Y⁻ may be, for example,bis(trifluoromethanesulfonyl)imide (TFSI⁻),bis(fluoromethanesulfonyl)imide, BF₄ ⁻, or CF₃SO₃ ⁻.

The polymer ionic liquid may include, for example, a cation includingpoly(1-vinyl-3-alkylimidazolium), poly(1-allyl-3-alkylimidazolium), orpoly(1-(methacryloxy-3-alkylimidazolium) and an anion including CH₃COO⁻,CF₃COO⁻, CH₃SO₃ ⁻, CF₃SO₃ ⁻, (CF₃SO₂)₂N⁻, (FSO₂)₂N⁻, (CF₃SO₂)₃C⁻,(CF₃CF₂SO₂)₂N⁻, C₄F₉SO₃ ⁻, C₃F₇COO⁻, or (CF₃SO₂)(CF₃CO)N⁻. A combinationcomprising at least one of the foregoing may also be used.

The compound represented by Formula 22 may bepolydiallyldimethylammonium bis(trifluoromethanesulfonyl)imide.

In some embodiments, the polymeric ionic liquid may include alow-molecular weight polymer, a thermally stable ionic liquid, and alithium salt. The low-molecular weight polymer may have an ethyleneoxide chain. The low-molecular weight polymer may be a glyme. Forexample, the glyme may include polyethylene glycol dimethylether(polyglyme), tetraethylene glycol dimethyl ether (tetraglyme),triethylene glycol dimethylether (triglyme), or a combination thereof. Aweight average molecular weight of the low-molecular weight polymer maybe in a range of about 75 Daltons to about 2,000 Daltons, for example,about 250 Daltons to about 500 Daltons. The thermally stable ionicliquid may be the same as those listed above in conjunction with theabove-described ionic liquid. The lithium salt may be any suitablecompound of which an alkali metal is lithium from among theaforementioned lithium salts.

The protective film may further include an oligomer. For example, theoligomer in the protective film may include polyethylene glycol dimethylether, polyethylene glycol diethyl ether, and a combination thereof. Aweight average molecular weight of the oligomer may be in a range ofabout 200 Daltons to about 2,000 Daltons, or about 300 Da to about 1800Da, or about 400 Da to about 1500 Da, and a content of the oligomer maybe in a range of about 5 parts by weight to about 50 parts by weight, orabout 10 parts by weight to about 40 parts by weight, or about 10 partsby weight to about 30 parts by weight, based on 100 parts by weight ofthe particle of the protective film. When such an oligomer is added, theprotective film may have improved film formability, mechanicalproperties, and ion conductivity.

An ion conductivity of the protective film may be, at a temperature ofabout 25° C., 1×10⁻⁴ Siemens per centimeter (S/cm) or greater, 5×10⁻⁴S/cm or greater, or 1×10⁻³ S/cm or greater.

The nitrogen-containing additive included in the protective film mayinclude an inorganic nitrate, an organic nitrate, an inorganic nitrite,an organic nitrite, an organic nitro compound, an organic nitrosocompound, a N—O compound, a lithium nitride (Li₃N), or a combinationthereof.

For example, the inorganic nitrate may include lithium nitrate,potassium nitrate, cesium nitrate, barium nitrate, ammonium nitrate, ora combination thereof. For example, the organic nitrate may includedialkyl imidazolium nitrate, guanidine nitrate, ethyl nitrate, propylnitrate, butyl nitrate, pentyl nitrate, octyl nitrate, or a combinationthereof. For example, the organic nitrite may include ethyl nitrite,propyl nitrite, butyl nitrite, pentyl nitrite, octyl nitrite, or acombination thereof.

For example, the organic nitroso compound may include nitromethane,nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitrotoluene,dinitrotoluene, nitropyridine, or a combination thereof. For example,the N—O compound may include pyridine N-oxide, alkylpyridine N-oxide,tetramethyl piperidine N-oxyl (TEMPO), or a combination thereof.

In some embodiments, the nitrogen-containing additive in the protectivefilm may include LiNO₃, Li₃N, or a combination thereof, and the metalsalt containing a Group 1 or 2 element in the protective film mayinclude cesium bis(trifluoromethylsulfonyl)imide (CsTFSI), CsNO₃, CsPF₆,CsFSI, CsAsF₆, CsClO₄, CsBF₄, or a combination thereof. For example, themetal salt may be CsTFSI.

An amount of the metal salt containing a Group 1 or 2 element and thenitrogen-containing additive in the protective film may be in a range ofabout 0.1 parts by weight to about 100 parts by weight, for example,about 0.1 parts by weight to about 50 parts by weight, or about 0.1parts by weight to about 30 parts by weight, based on 100 parts byweight of the particle. When the content of the metal salt containing aGroup 1 or 2 element and the nitrogen-containing additive is within anyof these ranges, the lithium metal battery may have a lithium dendriticgrowth suppression effect, a reduced interfacial resistance between asurface of the lithium metal negative electrode and the protective film,and improved lithium ion mobility.

The protective film may include, for example, a metal salt containing aGroup 1 or 2 element other than the composite electrolyte. A content ofthe metal salt containing a Group 1 or 2 element may be in a range ofabout 0.1 parts by weight to about 100 parts by weight, or about 0.1parts by weight to about 50 parts by weight, or for example, about 0.1parts by weight to about 30 parts by weight, based on 100 parts byweight of the particle.

The protective film may include, for example, a nitrogen-containingadditive other than the composite electrolyte. An amount of thenitrogen-containing additive may be in a range of about 0.1 parts byweight to about 100 parts by weight, or for example, or about 0.1 partsby weight to about 50 parts by weight or about 0.1 parts by weight toabout 30 parts by weight, based on 100 parts by weight of the particle.

The protective film may include, for example, a metal salt containing aGroup 1 or 2 element and a nitrogen-containing additive other than thecomposite electrolyte. A content of the metal salt containing a Group 1or 2 element may be in a range of about 0.01 part by weight to about99.99 parts by weight, or about 0.1 part by weight to about 50 parts byweight, or for example, about 0.1 part to about 30 parts by weight, anda content of the nitrogen-containing additive may be in a range of about0.01 part by weight to about 99.99 parts by weight, or for example, orabout 0.1 part by weight to about 50 parts by weight, or about 0.1 partby weight to about 30 parts by weight, based on 100 parts by weight ofthe particle. A mixed weight ratio of the metal salt containing a Group1 or 2 element to the nitrogen-containing additive in the protectivefilm may be in a range of about 1:9 to about 9:1, about 1:5 to about5:1, or about 1:2 to about 2:1, or in some embodiments, about 1:1. Whenthe mixed weight ratio of the metal salt containing a Group 1 or 2element to the nitrogen-containing additive is within any of theseranges, due to good deposition density on a surface of the lithium metalnegative electrode and improved lithium ion mobility characteristics inthe electrolyte, the lithium metal battery may have improved ratecapability and lifespan characteristics.

The protective film may have excellent mechanical strength andflexibility, thus effectively suppressing formation of lithium dendrite.An ion conductive thin film having a high ion conductivity may bebetween a lithium metal negative electrode and a protective film. Theion conductive thin film may increase ion conductivity and lithium ionmobility of the protective film; thus an interfacial resistance betweenthe lithium metal negative electrode and the protective film maydecrease. The ion conductive thin film may include, for example, lithiumnitride (Li₃N).

The protective film may also chemically improve a deposition/dissolutionprocess of lithium ions to thereby improve deposition morphology of thelithium metal negative electrode, as compared with a case of forming aconventional protective film, and consequently increase depositiondensity on a surface of the lithium metal negative electrode and lithiumion mobility (or transference number). In addition, as described above,a metal salt containing a Group 1 or 2 element, a nitrogen-containingadditive, or a combination thereof may be confined to the protectivefilm on a surface of the lithium metal negative electrode, and thus maybe unlikely to be dispersed in the liquid electrolyte or to migratetoward the positive electrode and react with the positive electrode. Inconclusion, it may be possible to manufacture a lithium metal batterywith high rate characteristics and lifespan characteristics.

According to another example embodiment, a protected negative electrodemay include a lithium metal negative electrode including lithium metalor a lithium metal alloy; and a protective film on the lithium metalnegative electrode.

When the protected negative electrode includes the protective film, thevolumetric change of the lithium metal negative electrode and lithiumdendritic growth may be suppressed.

Referring to FIGS. 4A to 4D, the structure of a negative electrode for alithium metal battery according to one or more embodiments will bedescribed in detail. Referring to FIG. 4A to 4D, a particle 13 of aprotective film 12 may have a microspherical shape.

Referring to FIG. 4A, a protected negative electrode 20 includes alithium metal electrode 11 and the protective film 12 on the lithiummetal electrode 11, the lithium metal electrode 11 being on a currentcollector 10 and including lithium metal or a lithium metal alloy. Theprotective film 12 includes the particle 13. Gaps (i.e., space) arepresent between the particles 13, and ions may be transported throughthese gaps. Thus, when such a protective film 12 is used, the negativeelectrode may have improved ion conductivity. Furthermore, the gaps, forexample, the pore structure between the particles 13, may provide aspace for lithium dendritic growth and act as a guide for growth oflithium dendrites. Although it is not illustrated in the drawings, asthe particle 13 is positively charged, anions may be confined to thevicinity of the particle 13, and thus migration of anions may besuppressed and/or prevented. Without being limited by theory it isunderstood that this consequently results in an increase of lithium ionmigration and prevention of a side reaction between anions and thelithium metal electrode.

The lithium metal alloy 11 may include lithium metal, a metal/metalloidalloyable with lithium metal, an oxide thereof, or a combinationthereof. Examples of the metal/metalloid alloyable with lithium metal oran oxide thereof include Si, Sn, Al, Ge, Pb, Bi, Sb, a Si—Y alloy(wherein Y is an alkaline metal, an alkaline earth metal, a Group 13element, a Group 14 element, a Group 15 element, a Group 16 element, atransition metal, a rare earth element, or a combination thereof, exceptfor Si), a Sn—Y alloy (wherein Y is an alkaline metal, an alkaline earthmetal, a Group 13 element, a Group 14 element, a Group 15 element, aGroup 16 element, a transition metal, a rare earth element, or acombination thereof, except for Sn), MnO_(x) (wherein 0<x≤2), or acombination thereof.

Y may be magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba),radium (Ra), scandium (Sc), yttrium (Y), titanium (Ti), zirconium (Zr),hafnium (Hf), rutherfordium (Rf), vanadium (V), niobium (Nb), tantalum(Ta), dubnium (Db), chromium (Cr), molybdenum (Mo), tungsten (W),seaborgium (Sg), technetium (Tc), rhenium (Re), bohrium (Bh), iron (Fe),lead (Pb), ruthenium (Ru), osmium (Os), hassium (Hs), rhodium (Rh),iridium (Ir), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag),gold (Au), zinc (Zn), cadmium (Cd), boron (B), aluminum (Al), gallium(Ga), tin (Sn), indium (In), thallium (Tl), germanium (Ge), phosphorus(P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium(Se), tellurium (Te), polonium (Po), or a combination thereof. Examplesof the oxide of a metal/metalloid alloyable with lithium metal include alithium titanium oxide, a vanadium oxide, a lithium vanadium oxide,SnO₂, and SiO_(x) (wherein 0<x<2).

Referring to FIG. 4B, an ion conductive polymer 14 surrounds theparticle 13. Although it is not illustrated in the drawings, a liquidelectrolyte may be present in the gaps (i.e., space) between theparticles 13. The ion conductive polymer 14 included in the protectivefilm 12 may improve the strength of the protective film 12 and serve asa binder.

An amount of the ion conductive polymer may be 10 parts by weight orless, 5 parts by weight or less, or 2 parts by weight or less, based on100 parts by weight of the particle. A content of the ion conductivepolymer may be in a range of about 1 part by weight to about 10 parts byweight, about 1 part by weight to about 5 parts by weight, or about 1part by weight to about 2 parts by weight, based on 100 parts by weightof the particle. When an amount of the ion conductive polymer is withinany of these ranges, the protective film may have excellent mechanicalstrength and consequently may effectively suppress lithium dendriticgrowth.

The ion conductive polymer may serve as a binder in the protective filmwhich helps a particle be fixed on the lithium metal electrode. The ionconductive polymer may be any suitable material that may improvemechanical strength of the protective film. The ion conductive polymermay be, for example, any suitable ion conductive polymer, generally usedin a lithium metal battery, including a homopolymer, a copolymer, acrosslinked polymer, or a combination thereof.

The copolymer may be a block copolymer, a random copolymer, a graftcopolymer, an alternating copolymer, or a combination thereof.

The crosslinked polymer may be any polymer that has a linking bondbetween two different polymer chains. For example, the crosslinkedpolymer may be a polymer formed by crosslinking polymers having acrosslinkable functional group. The crosslinked polymer may be acrosslinked material obtained from a copolymer containing a repeatingunit having a crosslinkable functional group.

The crosslinked polymer may be a crosslinked material of a blockcopolymer including a polyethylene oxide block and a polystyrene blockhaving an acrylate functional group; or a crosslinked material of acompound including at least one selected from a (C₁-C₉ alkyl)(meth)acrylate, a (C₂-C₉ alkenyl) (meth)acrylate, a (C₁-C₁₂ glycol)diacrylate, a poly(C₂-C₆ alkylene glycol) diacrylate, and a polyolpolyacrylate. The C₁-C₉ alkyl (meth)acrylate may be, for example, hexylacrylate, 2-ethyl hexyl acrylate or allyl methacrylate.

Examples of the glycol diacrylate include 1,4-butanediol diacrylate,1,3-butylene glycol diacrylate, a 1,6-hexanediol diacrylate, an ethyleneglycol diacrylate, neopentyl glycol diacrylate, or a combinationthereof. Examples of the poly(alkylene glycol) diacrylate includediethylene glycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, tripropylene glycol diacrylate,polyethylene glycol diacrylate, polypropylene glycol diacrylate, or acombination thereof.

Examples of the polyol polyacrylate include trimethylol propanetriacrylate, pentaerythritol tetraacrylate, or pentaerythritoltriacrylate, or a combination thereof.

The ion conductive polymer may be, for example, a polystyrenehomopolymer or copolymer, a block copolymer including a styrene-basedrepeating unit, or a combination thereof. For example, the ionconductive polymer may include polystyrene homopolymer, apoly(styrene-divinylbenzene) block copolymer, a poly(styrene-isoprene)block copolymer, a poly(styrene-isoprene-styrene) block copolymer, apoly(styrene-butadiene) block copolymer, apoly(styrene-butadiene-styrene) block copolymer, apoly(styrene-ethylene-butylene-styrene) block copolymer, apoly(styrene-methylmethacrylate) block copolymer, apoly(styrene-acrylonitrile) block copolymer, apoly(styrene-vinylpyridine) block copolymer, apoly(acrylonitrile-butadiene-styrene) copolymer, apoly(acrylonitrile-ethylene-propylene-styrene) copolymer, a poly(methylmethacrylate-acrylonitrile-butadiene-styrene) copolymer, a poly(C₁-C₉alkyl) methacrylate-butadiene-styrene) copolymer, a poly(styrene-(C₁-C₉alkyl) acrylate) copolymer, poly(acrylonitrile-styrene-acrylate)copolymer, or a combination thereof.

Examples of the poly(C₁-C₉ alkyl) methacrylate-butadiene-styrene)copolymer include a polymethacrylate-butadiene-styrene) copolymer.Examples of the poly(styrene-(C₁-C₉ alkyl) acrylate) copolymer include apoly(styrene-acrylate) copolymer.

The poly(styrene-divinylbenzene) copolymer may be represented by Formula23:

In Formula 1, a and b as mole fractions may each independently be in arange of about 0.01 to about 0.99, wherein a sum of a and b may be equalto 1. In Formula 1, a may be, for example, in a range of about 0.95 toabout 0.99, for example, about 0.96 to about 0.99, or for example, about0.98 to about 0.99, and b may be, for example, in a range of about 0.01to about 0.05, for example, about 0.01 to about 0.04, or for example,about 0.01 to about 0.02.

The poly(styrene-divinylbenzene) copolymer may be represented by Formula23a:

The poly(styrene-divinylbenzene) copolymer may be represented by Formula23b:

The poly(acrylonitrile-butadiene-styrene) copolymer may be representedby Formula 24:

In Formula 24, x, y, and z as mole fractions may each independently bein a range of about 0.01 to about 0.99, wherein a sum of x, y, and z maybe equal to 1. In Formula 24, x may be in a range of about 0.1 to about0.35, y may be in a range of about 0.05 to about 0.55, and z may be in arange of about 0.2 to about 0.7. For example, x may be in a range ofabout 0.15 to about 0.35, y may be in a range of about 0.05 to about0.3, and z may be in a range of about 0.4 to about 0.6.

The poly(styrene-divinylbenzene) copolymer represented by Formula 23 andthe poly(acrylonitrile-butadiene-styrene) copolymer represented byFormula 24 may each have a degree of polymerization in a range of about2 to about 5,000, or for example, or about 2 to about 2,500, or about 5to about 1,000.

For example, the poly(styrene-divinylbenzene) copolymer represented byFormula 23 and the poly(acrylonitrile-butadiene-styrene) copolymerrepresented by Formula 24 may each be a block copolymer.

Referring to FIGS. 4A and 4B, the protective film 12 may be on thelithium metal negative electrode 11, and include an assembly of theparticles 13 as a monolayer. The particles 13 may be a monodisperselayer with substantially no particle agglomeration. The particles 13 maybe regularly or irregularly arranged on the lithium metal negativeelectrode 11. The particles 13 may be arranged periodically ornon-periodically on the lithium metal negative electrode 11. As shown inFIG. 4B, the ion conductive polymer 14 may surround the particle.

Referring to FIG. 4C, the protective film 12 is on the lithium electrodenegative electrode 11, and has a stacked structure of two monolayers ofthe particle 13. The ion conductive polymer 14 surrounds the particle13. That is, the protective film 12 may include a stacked assembly of aplurality of particle 13 monolayers on the lithium metal negativeelectrode 11. The number of stacked layers is dependent upon a desiredfinal thickness of the protective film 12. For example, the number ofthe stacked layers may be in a range of about 2 to about 100, or about 2to about 50, or about 5 to about 50.

Referring to FIG. 4D, in a protected negative electrode 20, theprotective film 12 may have a multi-layered structure including amixture of particles of different sizes 13 a, 13 b, and 13 c. When theprotective film 12 has a multi-layered structure including a mixture ofparticles of different sizes 13 a, 13 b, and 13 c, a porosity of theprotective film 12 may decrease, and/or a packing density of theprotective film 12 may increase. Thus, space for dendritic growth maydecrease, or a contact area between an electrolyte and the lithium metalnegative electrode 11 may decrease. Consequently, dendritic growth maybe effectively suppressed.

The particle 13 of the protective film 12 may include, for example, apoly(styrene-divinylbenzene) copolymer. When the particles 13 in theprotective film 12 are formed of a crosslinked polymer, the particles 13may be covalently linked to one another. The particles 13 may have astructure in which the particles 13 are covalently linked to oneanother. Thus, the protective film 12 may form a high-strength networkstructure. A porosity of the protective film 12 may be in a range ofabout 25% to about 50%, for example, about 28% to about 48%, or forexample, about 30% to about 45%. A pore size and porosity of theprotective film 12 may be based on the size of the particle 13. In theprotective film 12, substantially no agglomeration of the particles 13may occur, so that the protective film 12 may have a uniform thickness.A thickness of the protective film 12 may be in a range of about 1 μ μmto about 10 μm, about 2 μm to about 9 μm, or about 3 μm to about 8 μm. Athickness deviation of the protective film 12 may be in a range of about0.1 μm to about 4 μm, about 0.1 μm to about 3 μm, or about 0.1 μm toabout 2 μm.

FIGS. 4E and 4F each an enlarged view of an interface between theprotected negative electrode 20 and an electrolyte for illustratingoperational effect of the protected negative electrode 20.

Referring to FIG. 4E, in the protected negative electrode 20, a solidelectrolyte interface (SEI) 15 is on the lithium metal negativeelectrode 11, and the protective film 12 including the particle 13 is onthe SEI 15. The gaps (i.e., spaces) between the particles 13 may befilled with the liquid electrolyte 18. The tensile modulus of theparticle 13 is higher than the tensile modulus of the lithium metalnegative electrode 11, and thus, the lithium metal negative electrode 11and the SEI 15 may be more flexible than the particle 13. Accordingly,the particle 13 may press against the lithium metal negative electrode11 and the SEI 15. Thus, a groove may be formed on the lithium metalnegative electrode 11 and the SEI 15. The particle 13 may be, forexample, a crosslinked poly(styrene-divinylbenzene) copolymermicrosphere. Due to the force of the particle 13 on the lithium metalnegative electrode 11 and the SEI 15, lithium dendritic growth from thelithium metal negative electrode 11 may be suppressed, and in addition,a lithium dendrite which does form may be guided to the gaps (i.e.,space) between the particles 13.

Referring to FIG. 4F, after charging the battery, in the protectednegative electrode 20, a lithium deposition layer 16 may be formed onthe lithium metal negative electrode 11 by lithium deposition. Thus, theprotected negative electrode 20 may have a structure in which theprotective film 12 contains the SEI 13 and the particle 13 on thelithium deposition layer 16.

The protected negative electrode 20 including the protective film 12including the particle, 13 may have a significantly increased lithiumdeposition density. Therefore, volumetric change, e.g., thicknesschange, of the protected negative electrode 20 may be suppressed. Inaddition, the protective film 12 may have a network structure and/orporous structure to thereby provide space for dendritic growth. Thus,irregular dendritic growth may be suppressed, and side products from apositive electrode may be effectively deposited. In addition, since theparticle 13 included in the protective film 12 may be positivelycharged, anions may be localized or confined to the vicinity of theparticle 13. Thus, migration of anions may be suppressed and/orprevented. Accordingly, a side reaction between the anions and thelithium metal negative electrode 11 may be suppressed, and a lithium iontransference number (T_(Li+)) may increase to thereby suppress lithiumdendritic growth. Consequently, a lithium metal battery employing theprotected negative electrode 20 may have improved lifespan and stabilityat a high temperature. For example, upon charging the battery, a lithiumdeposition density on a surface of the lithium metal electrode may be ina range of about 0.2 grams per cubic centimeter (g/cm³) to about 0.4g/cm³, about 0.3 g/cm³ to about 0.4 g/cm³, about 0.3 g/cm³ to about 0.35g/cm³, or about 0.32 g/cm³ to about 0.35 g/cm³.

Referring to FIGS. 4G to 4I, a crosslinked product of a polymerizableoligomer 17 may be between the particles 13 in the protective film 12.The protected negative electrode 20 illustrated in FIGS. 4G to 4Icorresponds to the protected negative electrode 20 illustrated in FIGS.4A to 4C, but in which the gaps (i.e., space) between the particles 13of the protective film 12 are filled with the crosslinked product of apolymerizable oligomer 17. Since the crosslinked product of apolymerizable oligomer 17 is present in the empty space between theparticles 13, the protective film 12 may be formed as a single body.Consequently, the protective film 12 may have excellent mechanicalproperties. Therefore, when such a protective film 12 is used, it may behighly effective to suppress lithium dendritic growth on a surface ofthe protected negative electrode 20. Further, the lithium metal batterymay also have improved lithium deposition density upon charging anddischarging and improved conductivity. In the case that the crosslinkedproduct of a polymerizable oligomer 17 is ionically conductive, ions maybe transferred through the crosslinked material of a polymerizableoligomer 17. Therefore, the protected negative electrode 20 includingthe protective film 12 may have improved ion conductivity. In addition,since the particle 13 included in the protective film 12 is positivelycharged, a lithium ion transference number may be greatly increased.

According to another example embodiment, a lithium metal battery mayinclude a positive electrode; a protected negative electrode including alithium metal negative electrode including a lithium metal or a lithiummetal alloy, and a protective film on the lithium metal negativeelectrode; and an electrolyte between the positive electrode and theprotected negative electrode, wherein the protective film includes acomposite electrolyte, including a particle comprising a positivelycharged particle, a particle that is positively charged by having acoordinate bond with a cation, or a combination thereof; and a lithiumsalt.

Referring to FIG. 5A, a lithium metal battery 30 includes a positiveelectrode 21, a protected negative electrode 20, and an electrolyte 24between the positive electrode 21 and the protected negative electrode20. The protected negative electrode 20 may include the lithium metalnegative electrode 11 and the protective film 12.

As the lithium metal battery 30 includes the protected negativeelectrode 20 containing a positively charged particle (not illustrated),a side reaction between the protected negative electrode 20 and theelectrolyte 24 may be suppressed, and deposition/stripping reactions ofthe lithium metal negative electrode 11 may be more likely to bereversible. Thus, lithium dendritic growth at an interface between theprotected negative electrode 20 and the electrolyte 24 may besuppressed, and a deposition density of the lithium deposition layerformed on the lithium metal negative electrode 11 may increase.Accordingly, volumetric change of the lithium metal battery 30 may besuppressed. Consequently, lifespan characteristics of the lithium metalbattery 30 may improve.

The electrolyte 24 of the lithium metal battery 30 may include thecomposite electrolyte described above. Since the electrolyte 24 includesthe composite electrolyte, migration of lithium ions between thepositive electrode 21 and the protected negative electrode 20 may befacilitated. Thus, an internal resistance of the lithium metal battery30 may decrease to thereby further improve charge and dischargecharacteristics of the lithium metal battery 30. The compositeelectrolyte may be a liquid electrolyte, a solid electrolyte, or a gelelectrolyte.

The electrolyte of the lithium metal battery 30 may include a liquidelectrolyte, a solid electrolyte, a gel electrolyte, a polymeric ionicliquid, or a combination thereof. The lithium metal battery 30 mayinclude a separator.

Referring to FIGS. 5B to 5D, depending on a desired energy density,current capacity, lifespan, or the like, of the lithium metal battery30, the electrolyte 24 may have a monolayer structure and/or amulti-layered structure.

Referring to FIG. 5B, the electrolyte 24 has a monolayer structureincluding a first liquid electrolyte layer 24 a in contact with theprotective film 12 of the protected negative electrode 20. A firstliquid electrolyte included in the first liquid electrolyte layer 24 amay have a composition identical to or different from a composition ofthe liquid electrolyte included in the protective film 12.

Referring to FIG. 5C, the electrolyte 24 has a monolayer structureincluding a separator 24 c in contact with the protective film 12 of theprotected negative electrode 20 and the first liquid electrolyte layer24 a. The separator 24 c may be a multi-layer separator includingpolyethylene, polypropylene, polyvinylidene fluoride, or a combinationthereof. For example, the separator 24 c may be a two-layer separatorincluding polyethylene/polypropylene, a three-layer separator includingpolyethylene/polypropylene/polyethylene, or a three-layer separatorincluding polypropylene/polyethylene/polypropylene. However, embodimentsare not limited thereto. Any suitable separator used in the preventionof a short circuit between a positive electrode and a negative electrodemay be used as the separator 24 c.

Referring to FIG. 5D, the electrolyte 24 may have a multi-layerstructure including the separator 24 c in contact with the protectivefilm 12 of the protected negative electrode 20, and the first liquidelectrolyte layer 24 a containing a first liquid electrolyte added toand impregnated in the separator 24 c; a second solid electrolyte layer24 e in contact with the first liquid electrolyte layer 24 a/separator24 c and including a ceramic conductor; and a second liquid electrolytelayer 24 b in contact with the second solid electrolyte layer 24 e andincluding a second liquid electrolyte. The positive electrode 21 may becompletely separated from the protected negative electrode 20 by thesecond solid electrolyte layer 24 e, and the protected negativeelectrode 20 may also be completely separated from the second solidelectrolyte layer 24 e by the first liquid electrolyte layer 24 a,thereby suppressing a side reaction. Thus, when the lithium metalbattery 30 includes an electrolyte having such a multi-layer structure,the lithium metal battery 30 may have significantly improved lifespancharacteristics. In some embodiments, the first liquid electrolyte maybe an anolyte, and the second liquid electrolyte may be a catholyte. Acomposition of the first liquid electrolyte may be identical to ordifferent from that of the second liquid electrolyte.

Referring to FIG. 5E, the electrolyte 24 may have a multi-layerstructure including a first solid electrolyte layer 24 d in contact withthe protective film 12 of the protected negative electrode 20, andincluding a composite electrolyte; the second solid electrolyte layer 24e in contact with the first solid electrolyte layer 24 d and including aceramic conductor; and the second liquid electrolyte layer 24 b incontact with the second solid electrolyte layer 24 e. The protectivefilm 12 may include a liquid electrolyte.

Referring to FIG. 5F, the electrolyte 24 may have a multi-layerstructure including a first solid electrolyte layer 24 d in contact withthe protective film 12 of the protected negative electrode 20 andincluding a composite electrolyte; the separator 24 c in contact withthe first solid electrolyte layer 24 d; the first liquid electrolytelayer 24 a containing a first liquid electrolyte impregnated in theseparator 24 c; the second solid electrolyte layer 24 e in contact withthe first liquid electrolyte layer 24 a and including a ceramicconductor; and the second liquid electrolyte layer 24 b in contact withthe second solid electrolyte layer 24 e.

Referring to FIG. 5G, the electrolyte 24 may have a multi-layerstructure including the second solid electrolyte layer 24 e in contactwith the protective film 12 of the protected negative electrode 20 andincluding a ceramic conductor; and the second liquid electrolyte layer24 b in contact with the second solid electrolyte layer 24 e.

Upon charging and discharging of the lithium metal battery, a change inthickness of a protected negative electrode after charging anddischarging may be less than a change in thickness of a protectednegative electrode including a protected film including a particle thatis not positively charged.

Upon charging and discharging of the lithium metal battery, when theprotected negative electrode includes the positively charged particle,it may be possible to suppress a side reaction at an interface between aprotected negative electrode and an electrolyte and to increase thereversibility of deposition/stripping reactions which may occur, andthereby suppress a change in thickness of the protected negativeelectrode. In contrast, a lithium metal battery in which a protectednegative electrode includes a protective film including a particle thatis not positively charged, during charging and discharging, a sidereaction between anions and lithium at an interface between a protectednegative electrode and an electrolyte may increase, and thereversibility of deposition/stripping reactions may be deteriorated tothereby increase a change in the thickness of the protected negativeelectrode. Consequently, a lithium metal battery including a protectednegative electrode including a protective film including a particle thatis not positively charged may have deteriorated cycle characteristics.

A lithium metal battery including the protected negative electrode maybe manufactured as follows.

First, a negative electrode including lithium metal and a protectednegative electrode including a protective film may be prepared.

A lithium metal thin film may be used as the negative electrodeincluding lithium metal. In some embodiments, a negative electrodeincluding lithium metal may include a current collector and a negativeactive material layer on the current collector. For example, thenegative electrode including lithium metal may be used in a state inwhich a lithium metal thin film is on a conductive substrate, i.e., acurrent collector. The lithium metal thin film and the current collectormay be formed as a single body.

The current collector in the negative electrode including lithium metalmay include stainless steel, copper, nickel, iron, cobalt, or acombination thereof, but the current collector is not limited thereto,and any metallic substrate having excellent electrical conductivity maybe used. For example, the current collector may be a conductive oxidesubstrate or a conductive polymer substrate. Also, the current collectormay have a structure such as a surface of an insulating substrate coatedwith a conductive metal, a conductive metal oxide, a conductive polymer,or a combination thereof, or may be a whole substrate formed of aconductive material. However the structure of the current collector isnot limited thereto. For example, the current collector may be aflexible substrate. Thus, the current collector may be easily bent.Also, once it is bent, the current collector may be easily restored toits original shape.

In addition, the negative electrode including lithium metal may includean additional negative active material other than a lithium metal. Thenegative electrode may be an alloy of lithium metal with anothernegative active material, a composite of lithium metal with anothernegative active material, or a mixture of lithium metal with anothernegative active material.

The additional negative active material that may be added to thenegative electrode may include, for example, a metal alloyable withlithium, a transition metal oxide, a non-transition metal oxide, acarbononaceous material, or a combination thereof.

Examples of the metal alloyable with lithium include silicon (Si), tin(Sn), aluminum (Al), germanium (Ge), lead (Pb), bismuth (Bi), antimony(Sb), a Si—Y alloy (wherein Y is an alkali metal, an alkaline earthmetal, a Group 13 element, a Group 14 element, a Group 15 element, aGroup 16 element, a transition metal, a rare earth element, or acombination thereof, and Y is not Si), and a Sn—Y alloy (wherein Y is analkali metal, an alkaline earth-metal, a Group 13 element, a Group 14element, a Group 15 element, a Group 16 element, a transition metal, arare earth element, or a combination thereof, and Y is not Sn), or acombination thereof. Y may be magnesium (Mg), calcium (Ca), strontium(Sr), barium (Ba), radium (Ra), scandium (Sc), yttrium (Y), titanium(Ti), zirconium (Zr), hafnium (Hf), rutherfordium (Rf), vanadium (V),niobium (Nb), tantalum (Ta), dubnium (Db), chromium (Cr), molybdenum(Mo), tungsten (W), seaborgium (Sg), technetium (Tc), rhenium (Re),bohrium (Bh), iron (Fe), lead (Pb), ruthenium (Ru), osmium (Os), hassium(Hs), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), copper(Cu), silver (Ag), gold (Au), zinc (Zn), cadmium (Cd), boron (B),aluminum (Al), gallium (Ga), tin (Sn), indium (In), germanium (Ge),phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S),selenium (Se), tellurium (Te), polonium (Po), or a combination thereof.

For example, the transition metal oxide may be a lithium titanium oxide,a vanadium oxide, or a lithium vanadium oxide.

For example, the non-transition metal oxide may be SnO₂ or SiO_(x)(wherein 0<x<2).

Examples of the carbonaceous material may include crystalline carbon,amorphous carbon, or a combination thereof. Examples of the crystallinecarbon may include graphite, such as natural graphite or artificialgraphite that are in shapeless, plate, flake, spherical, or fibrousform. Examples of the amorphous carbon may include soft carbon (carbonsintered at low temperatures), hard carbon, meso-phase pitch carbides,and sintered cokes. A combination comprising at least one of theforegoing may also be used.

A protective film may be on the negative electrode including lithiummetal.

The protective film may be prepared using a composite electrolyteincluding a particle, the particle including a positively chargedparticle, a particle having a coordinate bond with a cation, or acombination thereof, and a lithium salt.

In some embodiments, after a composite electrolyte is prepared, thecomposite electrolyte may be directly coated on a negative electrodeincluding lithium metal to prepare a protected negative electrode. Insome embodiments, the composite electrolyte may be cast on a separatesupport to form a film, which may then be separated from the support andlaminated on the negative electrode including lithium metal to obtain aprotected negative electrode. The form of the protected negativeelectrode is not limited to the foregoing description, and the protectednegative electrode may be in any suitable form for a lithium battery.For example, the protected negative electrode may be prepared byprinting a composition ink including a composite electrolyte on anegative electrode including lithium metal by inkjet printing or thelike.

The composite electrolyte may be prepared by mixing the particle and thelithium salt in an organic solvent. The organic solvent used in thecomposite electrolyte is not particularly limited, and may include,dimethyl aceteamide, dimethyl sulfoxide, or the like, or a combinationthereof.

Next, a positive electrode is prepared.

A positive active material, a conductive agent, a binder, and a solventare combined to prepare a positive active material composition. Thepositive active material composition may be directly coated on analuminum current collector and dried to prepare a positive electrodeplate having a formed positive active material layer. Alternatively, thepositive active material composition may be cast on a separate support,which then may be separated from the support and laminated on analuminum current collector to prepare a positive electrode plate havinga positive active material layer thereon.

The positive active material is not limited and may be any suitablepositive active material in the art, and for example, may be alithium-containing metal oxide. In one or more embodiments, the positiveactive material may include a composite oxide of lithium and a metalincluding cobalt, manganese, nickel, or a combination thereof. In one ormore embodiments, the positive active material may be a compoundrepresented by the following formulae: Li_(a)A_(1-b)B′_(b)D₂ (wherein0.90≤a≤1.8 and 0≤b≤0.5); Li_(a)E_(1-b)B′_(b)O_(2-c)D_(c) (wherein0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); LiE_(2-b)B′_(b)O_(4-c)D_(c) (wherein0≤b≤0.5 and 0≤c≤0.05); Li_(a)Ni_(1-b-c)Co_(b)B′_(c)D_(α) (wherein0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2);Li_(a)Ni_(1-b-c)Co_(b)B′_(c)O_(2-α)F′_(α) (wherein 0.90≤a≤1.8, 0≤b≤0.5,0≤c≤0.05, and 0<α<2); Li_(a)Ni_(1-b-c)Mn_(b)B′_(c)D_(α) (wherein0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2);Li_(a)Ni_(1-b-c)Mn_(b)B′_(c)O_(2-α)F′_(α) (wherein 0.90≤a≤1.8, 0≤b≤0.5,0≤c≤0.05, and 0<α<2); Li_(a)Ni_(b)E_(c)G_(d)O₂ (wherein 0.90≤a≤1.8,0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1); Li_(a)Ni_(b)Co_(c)Mn_(d)GeO₂(wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, and 0.001≤e≤0.1.);Li_(a)NiG_(b)O₂ (wherein 0.90≤a≤1.8 and 0.001≤b≤0.1); Li_(a)CoG_(b)O₂(wherein 0.90≤a≤1.8 and 0.001≤b≤0.1); Li_(a)MnG_(b)O₂ (wherein0.90≤a≤1.8 and 0.001≤b≤0.1); Li_(a)Mn₂G_(b)O₄ (wherein 0.90≤a≤1.8 and0.001≤b≤0.1.); QO₂; QS₂; LiQS₂; V₂O₅; LiV₂O₅; LiI′O₂; LiNiVO₄;Li_((3-f))J₂(PO₄)₃ (wherein 0≤f≤2); Li_((3-f))Fe₂(PO₄)₃ (wherein 0≤f≤2);LiFePO₄, or a combination thereof.

In the foregoing formulae, A may include nickel (Ni), cobalt (Co),manganese (Mn), or a combination thereof; B′ may include aluminum (Al),Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr),vanadium (V), a rare-earth element, or a combination thereof; D mayinclude oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or acombination thereof; E may include Co, Mn, or a combination thereof; F′may include F, S, P, or a combination thereof; G may include Al, Cr, Mn,Fe, Mg, lanthanum (La), cerium (Ce), Sr, V, or a combination thereof; Qmay include titanium (Ti), molybdenum (Mo), Mn, or a combinationthereof; I′ may include Cr, V, Fe, scandium (Sc), yttrium (Y), or acombination thereof; and J may include V, Cr, Mn, Co, Ni, copper (Cu),or a combination thereof.

For example, the positive active material may beLi_(a)Ni_(b)Co_(c)Mn_(d)O₂ (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and0≤d≤0.5), Li₂MnO₃, LiMO₂ (wherein M may be Mn, Fe, Co, or Ni),Li_(a)Ni_(b)Co_(c)Al_(d)O₂ (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and0≤d≤0.5), LiCoO₂, LiMn_(x)O_(2x) (wherein x=1 or 2),LiNi_(1-x)Mn_(x)O_(2x) (wherein 0<x<1), or LiFePO₄, or a combinationthereof.

The compounds listed above as positive active materials may have acoating layer on a surface thereof. Alternatively, a mixture of acompound without a coating layer and a compound having a coating layer,may be used. The above-mentioned compounds may be used. In one or moreembodiments, the coating layer may include a coating element includingan oxide, a hydroxide, an oxyhydroxide, an oxycarbonate, or ahydroxycarbonate of the coating element, or a combination thereof. Inone or more embodiments, the compound for the coating layer may beamorphous or crystalline. In one or more embodiments, the coatingelement for the coating layer may include magnesium (Mg), aluminum (Al),cobalt (Co), potassium (K), sodium (Na), calcium (Ca), silicon (Si),titanium (Ti), vanadium (V), tin (Sn), germanium (Ge), gallium (Ga),boron (B), arsenic (As), zirconium (Zr), or a combination thereof. Inone or more embodiments, the coating layer may be formed using anysuitable method that does not adversely affect the physical propertiesof the positive active material when the coating layer is present. Forexample, the coating layer may be formed using a spray coating method ora dipping method. The coating method is not limited and may be anymethod in the art, and thus a detailed description thereof will beomitted.

The conductive agent may include acetylene black, Ketjen black, naturalgraphite, artificial graphite, carbon black, acetylene black, carbonfiber, and metal powder and metal fiber of, e.g., copper, nickel,aluminum, silver, or a combination thereof. In some embodiments, aconductive material such as a polyphenylene derivative may be used aloneor in combination with an additional conductive agent, but embodimentsare not limited thereto. Any suitable conductive agent available in theart may be used.

Examples of the binder may include a vinylidenefluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF),polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene, astyrene-butadiene rubber polymer, or a combination thereof, butembodiments are not limited thereto. Any suitable material available asa binder may be used.

Examples of the solvent include N-methyl-pyrrolidone, acetone, water, ora combination thereof, but embodiments are not limited thereto. Anysuitable solvent in the art may be used.

The amounts of the positive active material, the conductive agent, thebinder, and the solvent may be determined by the person of skill in theart without undue experimentation. At least one of the conductive agent,the binder, and the solvent may be omitted according to the use and thestructure of the lithium battery.

Next, a separator to be disposed between the positive electrode and thenegative electrode is prepared.

The separator may be any suitable separator for use in a lithiumbattery. The separator may have low resistance to the migration of ionsin an electrolyte and may have electrolytic solution-retaining ability.Examples of the separator may include glass fiber, polyester,polyethylene, polypropylene, polytetrafluoroethylene (PTFE) (e.g.,Teflon™), or a combination thereof, each of which may be a non-woven orwoven fabric. For example, a rollable separator such as polyethylene,polypropylene, or the like may be used in a lithium ion battery. Forexample, a separator with excellent ability to retain an organicelectrolyte solution, may be used for a lithium ion polymer battery. Forexample, the separator may be manufactured in the following manner.

A polymer resin, a filler, and a solvent may be mixed together toprepare a separator composition. Then, the separator composition may bedirectly coated on an electrode, and then dried to form the separator.Alternatively, the separator composition may be cast on a support andthen dried to form a separator film, which may then be separated fromthe support and laminated on the electrode to form the separator.

The polymer resin used to manufacture the separator may be any suitablematerial that is used as a binder for electrode plates. Examples of thepolymer resin may include a vinylidene fluoride/hexafluoropropylenecopolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile,polymethylmethacrylate, or a combination thereof.

Next, a liquid electrolyte is prepared.

For example, an organic electrolyte solution may be prepared. Theorganic electrolyte solution may be prepared by dissolving a lithiumsalt in an organic solvent.

The organic solvent is not limited, and any suitable organic solvent fora lithium battery may be used. For example, the organic solvent may bepropylene carbonate, ethylene carbonate, fluoroethylene carbonate,vinylethylene carbonate, diethyl carbonate, methyl ethyl carbonate,methyl propyl carbonate, butylene carbonate, benzonitrile, acetonitrile,tetrahydrofuran, 2-methyl tetrahydrofuran, γ-butyrolactone, dioxolane,4-methyl dioxolane, N,N-dimethyl formamide, dimethyl aceteamide,dimethyl sulfoxide, dioxane, 1,2-dimethoxy ethane, sulfolane,dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methylisopropyl carbonate, succinonitrile, diethyl glycol dimethyl ether,tetraethylene glycol dimethyl ether, triethyl glycol dimethyl ether,polyethyl glycol dimethyl ether, ethyl propyl carbonate, dipropylcarbonate, dibutyl carbonate, diethylene glycol, dimethyl ether, or acombination thereof.

The lithium salt is not limited and may be any material suitable for alithium battery. For example, the lithium salt may include LiPF₆, LiBF₄,LiSbF₆, LiAsF₆, LiClO₄, LiCF₃SO₃, Li(CF₃SO₂)₂N, Li(FSO₂)₂N, LiC₄F₉SO₃,LiAlO₂, LiAlCl₄, LiN(C_(x)F_(2x+1)SO₂)(C_(y)F_(2y+1)SO₂) (wherein x andy may each be a natural number), LiCl, LiI, or a combination thereof.

Referring to FIG. 6 , the lithium metal battery 30 includes a positiveelectrode 31, a negative electrode 32, and a battery case 34 includingthe positive electrode 31 and the negative electrode 32. The positiveelectrode 31, the negative electrode 32, and a separator (not shown) maybe wound or folded, and then sealed in the battery case 34. An organicelectrolyte solution may be injected into the battery case 34, and thenthe battery case 34 may be sealed to thereby complete the manufacture ofthe lithium metal battery 30. The battery case 34 may be a cylindricaltype, a rectangular type, or a thin-film type. In FIG. 6 , the batterycase 34 is illustrated as a rectangular type, however, the battery casemay also be a flexible pouch type. Thus, the battery case 34 may be bentor elongated.

The positive electrode 31 may be a porous positive electrode. The porouspositive electrode may be include a plurality of pores, or may be anypositive electrode that allows permeation of a liquid electrolytethereinto by capillary action, or the like.

For example the porous positive electrode may include a positiveelectrode prepared by coating and drying a positive active materialcomposition including a positive active material, a conductive agent, abinder, and a solvent. The thus prepared positive electrode may includea plurality of pores between the positive active material particles. Theporous positive electrode may be impregnated with a liquid electrolyte.

In some embodiments, a positive electrode may include a liquidelectrolyte, a gel electrolyte, a solid electrolyte, or a combinationthereof. The liquid electrolyte, the gel electrolyte, and the solidelectrolyte may be any suitable electrolyte for use in a lithium metalbattery that does not react with the positive active material, and thusprevents deterioration of the positive active material during acharge/discharge process.

In one or more embodiments, a plurality of lithium metal batteries maybe stacked to form a battery pack, which may be used in a device havinglarge capacity and high power usage, for example, in a laptop computer,a smartphone, or an electric vehicle (EV).

The lithium metal battery is not particularly limited to a lithium ionbattery or a lithium polymer battery; the lithium metal battery may alsoinclude a lithium air battery, a lithium all-solid battery, or the like.

As used herein, substituted means that the compound or group issubstituted with at least one (e.g., 1, 2, 3, or 4) substituent. Thesubstituent may be added by the replacement of at least one hydrogenatom in a compound or group with another atom or a functional group. Thesubstituent may include a C₁-C₄₀ alkyl group, a C₂-C₄₀ alkenyl group, aC₂-C₄₀ alkynyl group, a C₃-C₄₀ cycloalkyl group, a C₃-C₄₀ cycloalkenylgroup, and a C₇-C₄₀ aryl group. When a functional group is “optionally”substituted, it means that the functional group may be substituted withsuch a substituent as listed above.

a and b in the term “C_(a)-C_(b)” as used herein refer to the number ofcarbons in a particular functional group. That is, a functional groupmay include from a to b carbon atoms. For example, “C₁-C₄ alkyl group”refers to an alkyl group having 1 to 4 carbon atoms, such as CH₃—,CH₃CH₂—, CH₃CH₂CH₂—, (CH₃)₂CH—, CH₃CH₂CH₂CH₂—, CH₃CH₂CH(CH₃)—, or(CH₃)₃C—.

As used herein, a particular radical may refer to a mono-radical or adi-radical depending on the context. For example, when a substituentneeds two binding sites to bind with the rest of the molecule, thesubstituent may be understood as a di-radical. For example, asubstituent specified as an alkyl group that needs two binding sites maybe a di-radical, such as —CH₂—, —CH₂CH₂—, or —CH₂CH(CH₃)CH₂—. The term“alkylene” clearly indicates that the radical is a di-radical.

The term “alkyl” as used herein refers to a branched or unbranchedsaturated, monovalent hydrocarbon group. In some embodiments, an alkylgroup may be substituted or unsubstituted. Non-limiting examples of thealkyl group may include a methyl group, an ethyl group, a propyl group,an iso-propyl group, a butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, a hexyl group, a cyclopropyl group, a cyclopentylgroup, a cyclohexyl group, and a cycloheptyl group, each of which mayoptionally be substituted or unsubstituted. In some embodiments, analkyl group may have 1 to 6 carbon atoms. Non-limiting examples of aC₁-C₆ alkyl group include a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, an isobutyl group, a sec-butylgroup, a pentyl group, a 3-pentyl group, and a hexyl group.

The term “alkenyl” or “alkylene” as used herein refers to a straight orbranched chain, monovalent hydrocarbon group including 2 to 20 carbonatoms, having at least one carbon-carbon double bond. Non-limitingexamples thereof include an ethenyl group, a 1-prophenyl group, a2-prophenyl group, a 2-methyl-1-prophenyl group, a 1-butenyl group, a2-butenyl group, a cycloprophenyl group, a cyclopentenyl group, acyclohexenyl group, and a cycloheptenyl group. For example, an alkenylgroup may be substituted or unsubstituted. In some embodiments, analkenyl group may have 2 to 40 carbon atoms.

The term “alkynyl” as used herein refers to a straight or branchedchain, monovalent hydrocarbon group including 2 to 20 carbon atoms,having at least one carbon-carbon triple bond. Non-limiting examplesthereof include an ethynyl group, a 1-propynyl group, a 1-butynyl group,and a 2-butynyl group. For example, an alkynyl group may be substitutedor unsubstituted. In some embodiments, an alkynyl group may have 2 to 40carbon atoms.

The term “cycloalkyl” refers to a monovalent group having one or moresaturated rings in which all ring members are carbon. For example, the“cycloalkyl” may be a cyclopropyl group, a cyclobutyl group, acyclopentyl group, or a cyclohexyl group.

The term “aromatic” refers to a ring or ring system with a conjugated πelectron system, and may refer to a carbocyclic aromatic group (e.g., aphenyl group), or a heterocyclic aromatic group (e.g., a pyridinegroup). For example, an aromatic ring system as a whole may include asingle ring or a fused polycyclic ring (i.e., a ring that sharesadjacent atom pairs).

The term “aryl” as used herein refers to a cyclic moiety in which allring members are carbon and at least one ring is aromatic, the moietyhaving the specified number of carbon atoms, specifically 6 to 24 carbonatoms, more specifically 6 to 12 carbon atoms. More than one ring may bepresent, and any additional rings may be independently aromatic,saturated or partially unsaturated, and may be fused, pendant,spirocyclic or a combination thereof. Non-limiting examples of the arylgroup include a phenyl group, a biphenyl group, a naphthyl group, aphenanthrenyl group, and a naphthacenyl group. In some embodiments, anaryl group may be substituted or unsubstituted.

The term “arylene” as used herein refers to a divalent group formed bythe removal of two hydrogen atoms from one or more rings of an arene,wherein the hydrogen atoms may be removed from the same or differentrings Examples of the arylene include —C₆H₅—O—C₆H₅—.

The term “heteroaryl” as used herein refers a monovalent carbocyclicring group that includes one or more aromatic rings, in which at leastone ring member (e.g., one, two or three ring members) is a heteroatom.For example, the heteroatom may be oxygen, sulfur, or nitrogen, butembodiments are not limited thereto. Non-limiting examples of theheteroaryl group include a furanyl group, a thienyl group, an imidazolylgroup, a quinazolinyl group, a quinolinyl group, an isoquinolinyl group,a quinoxalinyl group, a pyridinyl group, a pyrrolyl group, an oxazolylgroup, and an indolyl group.

The term “heteroarylene” as used herein refers to a divalent radicalformed by the removal of two hydrogen atoms from one or more rings of aheteroaryl moiety, wherein the hydrogen atoms may be removed from thesame or different rings (preferably the same ring), each of which ringsmay be aromatic or nonaromatic

The terms “aralkyl” or “alkylaryl” as used herein refers to an alkylgroup covalently linked to a substituted or unsubstituted aryl groupthat is linked to a compound. Non-limiting examples of the aralkyl oralkylaryl include a benzyl group, a 2-phenylethyl group, a3-phenylpropyl group, and a naphthylalkyl group.

The term “cycloalkenyl” as used herein refers to a monovalentnon-aromatic group having one or more rings and one or morecarbon-carbon double bond in the ring, wherein all ring members arecarbon (e.g., cyclopentyl and cyclohexyl).

The terms “heterocyclic group” as used herein refers to a non-aromaticring or ring system including at least one heteroatom in its cyclicbackbone.

The term “halogen” as used herein refers to a stable atom belonging toGroup 17 of the periodic table of elements, for example, fluorine,chlorine, bromine, iodine, or astatine. For example, the halogen atommay be fluorine and/or chlorine.

A weight average molecular weight of the polymer may be measured by gelpermeation chromatography (GPC) using a polystyrene standard.

Hereinafter example embodiments will be described in detail withreference to Examples and Comparative Examples. These examples areprovided for illustrative purposes only and are not intended to limitthe scope of the inventive concept.

EXAMPLES Preparation of Composite Electrolyte Example 1:PEO+MS-DEAE+Lithium Salt

Polyethylene oxide (PEO) was mixed with acetonitrile to obtain asolution of 5 weight percent (wt %) PEO in acetonitrile. To the PEOacetonitrile solution, a particle-containing mixture and lithiumbis(fluorosulfonyl) imide (LiFSI, LiN(SO₂F)₂) were added to prepare acomposite electrolyte-forming composition.

Anhydrous THF was added to a MS-DEAE microsphere (having an averagediameter of about 3 μm), in which a poly(styrene-divinylbenzene)copolymer particle is linked to the diethylamino ethylenyl grouprepresented by Formula 8 via a covalent bond, to thereby obtain theparticle-containing mixture. Here, the amount of the particle was about5 wt %.

A composite electrolyte-forming composition was prepared in which theamount of the particle was 15 parts by weight, based on 100 parts byweight of the PEO, and the amount of the LiFSI was 30 parts by weight,based on 100 parts by weight of the PEO.

The prepared composite electrolyte-forming composition was cast on amember, and acetonitrile and THF in the resultant was graduallyevaporated in an argon glove box for 24 hours at a temperature of about25° C., and subsequently, under vacuum at a temperature of 25° C., theresult was dried for 24 hours to prepare a composite electrolyte film.The thickness of the prepared composite electrolyte film was about 50μm.

Comparative Example 1: PEO+MS+Lithium Salt

A composite electrolyte in the form of a film was prepared insubstantially the same manner as in Example 1, except that apoly(styrene-b-divinylbenzene) block copolymer microsphere (having anaverage diameter of about 3 μm, EPR-PSD-3, available from EPRUINanoparticles & Microspheres Co., Ltd.) was used instead of the MS-DEAEmicrosphere.

The poly(styrene-b-divinylbenzene) block copolymer including apolystyrene block and a polydivinylbenzene block in a mixed ratio ofabout 9:1 by weight, had a weight average molecular weight of about100,000 Daltons.

Comparative Example 2: PEO+SiO₂+Lithium Salt

A composite electrolyte in the form of a film was prepared insubstantially the same manner as in Example 1, except that a silica(SiO₂) nanoparticle (having an average diameter of about 7 nm) was usedinstead of the MS-DEAE microsphere.

Comparative Example 3: PEO+Lithium Salt

A composite electrolyte in the form of a film was prepared insubstantially the same manner as in Example 1, except that the MS-DEAEmicrosphere was not added.

Manufacture of Protective Film and Protected Negative Electrode Example2: MS-DEAE+Lithium Salt Protective Film/Protected Negative Electrode

Anhydrous THF was added to a MS-DEAE microsphere (having an averagediameter of about 3 μm), in which a poly(styrene-divinylbenzene)copolymer particle is covalently linked to the diethylamino oxyethylenylgroup represented by Formula, to thereby obtain the particle-containingmixture. Here, the amount of the particle was about 5 wt %.

To the prepared particle-containing mixture, lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO₂F)₂) was added to prepare a protective film-formingcomposition. The amount of LiFSI was about 30 parts by weight, based onbased on 100 parts by weight of the particle.

The prepared protective film-forming composition was coated on a lithiummetal thin film (having a thickness of about 40 μm) to a thickness ofabout 3 μm using a doctor blade.

The coated resultant was dried at a temperature of about 25° C., andsubsequently, under vacuum at a temperature of about 40° C., the resultwas dried for about 24 hours to prepare a protected negative electrodein which a protective film was formed on a lithium metal thin film.

Example 3: MS-DEAE+Lithium Salt+DEGDA Crosslinked Material ProtectiveFilm/Protected Negative Electrode

Anhydrous THF was added to a MS-DEAE microsphere (having an averagediameter of about 3 μm), in which a poly(styrene-divinylbenzene)copolymer particle is covalently linked to the diethylamino oxyethylenylgroup represented by Formula 8, to thereby obtain theparticle-containing mixture. Here, the amount of the particle was about5 wt %.

To the prepared particle-containing mixture, lithium bis(fluorosulfonyl)imide (LiFSI, LiN(SO₂F)₂) was added to prepare a protective film-formingcomposition. The amount of LiFSI was about 30 parts by weight, based onbased on 100 parts by weight of the particle.

The prepared protective film-forming composition was coated on a lithiummetal thin film (having a thickness of about 40 μm) to a thickness ofabout 3 μm using a doctor blade.

The coated resultant was dried at a temperature of about 25° C., andsubsequently, under vacuum at a temperature of about 40° C., the resultwas dried for about 24 hours.

Diethylene glycol diacrylate (DEGDA) was dissolved in THF to prepare a30 wt % solution. In the solution, the amount of DEGDA was about 30parts by weight, based on 100 parts by weight of the microsphere. Thissolution was cast on the coated and dried resultant. The cast resultantwas dried at a temperature of about 25° C. for 12 hours, andsubsequently, the result was irradiated with ultraviolet (UV) light at atemperature of about 40° C. for 1 hour to prepare a protected negativeelectrode in which a protective film was formed, the protective filmincluding microspheres on a lithium metal thin film and a crosslinkedmaterial of DEGDA in gaps (i.e., space) between the microspheres. Theamount of DEGDA was about 20 parts by weight, based on 100 parts byweight of the MS-DEAE microsphere.

Comparative Example 4: MS+Lithium Salt Protective Film/ProtectedNegative Electrode

A protective film-type negative electrode having a formed protectivefilm was prepared in substantially the same manner as in Example 2,except that the protective film-forming composition was prepared using apoly(styrene-b-divinylbenzene) block copolymer microsphere (having anaverage diameter of about 3 μm, EPR-PSD-3, available from EPRUINanoparticles & Microspheres Co., Ltd.) instead of the MS-DEAEmicrosphere.

The block copolymer included a polystyrene block and apolydivinylbenzene block in a mixed ratio of about 9:1 by weight, andthe poly(styrene-b-divinylbenzene) copolymer had a weight averagemolecular weight of about 100,000 Daltons.

Comparative Example 5: Bare Lithium Negative Electrode

Lithium metal thin film (having a thickness of about 40 μm) was used asa negative electrode.

Manufacture of Lithium Metal Battery Example 4

A protected negative electrode, in which a protective film was formed ona lithium metal thin film, was prepared in substantially the same manneras in Example 2.

LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, a conductive agent (Super-P™; availablefrom Timcal Ltd.), PVDF, and N-methyl pyrrolidone were mixed together toprepare a positive active material layer-forming composition. In thepositive active material layer-forming composition, a mixed ratio ofLiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ to the conductive agent to PVDF was97:1.5:1.5 by weight. About 137 grams (g) of N-methyl pyrrolidone wasused for 97 g of LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂.

The positive active material layer-forming composition was coated on analuminum foil (having a thickness of about 15 μm) and then dried at 25°C., followed by drying the result at about 110° C. under vacuum tothereby prepare a positive electrode.

A polyethylene separator (having a porosity of about 48%) was disposedbetween the prepared positive electrode and a protected negativeelectrode (having a thickness of about 43 μm) to manufacture a lithiummetal battery in a pouch cell form.

A liquid electrolyte was injected into the gap between the positiveelectrode and the protected negative electrode. The liquid electrolytewas an electrolyte in which 1.0 molar (M) LiN(SO₂F)₂ (hereinafter,referred to as “LiFSI”) was dissolved in a mixed solvent of1,2-dimethoxyethane (DME) to 1,1,2,2-tetrafluoroethyl2,2,3,3-tetrafluoropropyl ether (TTE) in a ratio of 2:8 by volume.

Example 5

A lithium metal battery was manufactured in substantially the samemanner as in Example 4, except that the protected negative electrodeprepared in Example 3 was used instead of the protected negativeelectrode prepared in Example 2.

Comparative Example 6

A lithium metal battery was manufactured in substantially the samemanner as in Example 4, except that the protected negative electrodeprepared in Comparative Example 4 was used instead of the protectednegative electrode prepared in Example 2.

Comparative Example 7

A lithium metal battery was manufactured in substantially the samemanner as in Example 4, except that the lithium metal negative electrodeprepared in Comparative Example 5 was used instead of the protectednegative electrode prepared in Example 2.

Evaluation Example 1: Measurement of Lithium Ion Transference Number(T_(Li+)) of Composite Electrolyte

For each of the composite electrolyte films prepared in Example 1 andComparative Examples 1 to 3, a lithium ion transference number wasmeasured at a temperature of 60° C. by using a lithium symmetric celland an impedance analyzer (Solartron 1260A Impedance/Gain-Phase Analyzercoupled with Solartron 1287 Electrochemical Interface). A lithium iontransference number was derived using an alternating current (AC)impedance method combined with a steady-state current method. First, aninitial lithium interface resistance (Ro) was measured from an impedancespectrum in a frequency range of 0.1 hertz (Hz) to 100 kilohertz (kHz),and subsequently, a small direct current voltage (less than 30millivolts (mV)) was applied thereto until a steady-state current (Iss)was obtained (time=3,000 seconds). Finally, a steady-state lithiuminterfacial resistance (Rss) was measured from the impedance spectrum ina frequency range of 0.1 Hz to 100 kHz. A lithium ion transferencenumber was derived using the parameters obtained from the impedanceresponse and the steady-state current response. In the lithium symmetriccell, as a composite electrolyte film was disposed between lithiumelectrodes, the lithium symmetric cell had a Li/composite electrolyte/Listructure, followed by sealing in a coin-cell.

The measurement results are shown in Table 1.

TABLE 1 Lithium ion transference number (T_(Li+)) Comparative Example 30.13~0.15 Comparative Example 2 0.12~0.16 Comparative Example 10.13~0.16 Example 1 0.18~0.22

As shown in Table 1, the composite electrolyte of Example 1 was found tohave an improved lithium ion transference number, as compared with thecomposite electrolytes of Comparative Examples 1 to 3.

Accordingly, a lithium battery including the composite electrolyte ofExample 1 has a decreased interfacial resistance and/or interfaceresistance, thereby improving cycle characteristics of the lithiumbattery.

In particular, the composite electrolyte of Example 1 including thepositively charged particle had an improved lithium ion transferencenumber, as compared with the composite electrolyte of ComparativeExample 1 including the particle that does not have a positive charge(not positively charged).

Without being limited by theory, it is believed that the increase in thelithium ion transference number in the composite electrolyte of Example1 may have resulted from suppression and/or prevention of chargetransfer of anions of a lithium salt due to electrostatic attraction ofthe anions to the positively charged particle serving as a receptor ofanions, and which relatively facilitated migration of lithium ions. Incontrast, in the composite electrolyte of Comparative Example 1including the particle that is not positively charged, it is difficultto suppress and/or prevent migration of such anions.

Evaluation Example 2: Measurement of Lithium Ion Transference Number(T_(Li+)) of Protective Film

For each of the protected negative electrode prepared in Example 2 andthe lithium negative electrode prepared in Comparative Example 5, alithium ion transference number was measured at a temperature of 25° C.in substantially the same manner as in Evaluation Example 1 by using alithium symmetric cell and an impedance analyzer (Solartron 1260AImpedance/Gain-Phase Analyzer coupled with Solartron 1287Electrochemical Interface).

A polyethylene separator (having a porosity of about 48%) impregnatedwith a liquid electrolyte was disposed between protective films of apair of protected negative electrodes prepared in Example 2, followed bysealing. Accordingly, a lithium symmetric cell having a Li/protectivefilm/liquid electrolyte/protective film/Li structure was prepared.

As the protective film of the protected negative electrode of Example 2was impregnated with a liquid electrolyte, the protective film includesthe liquid electrolyte.

A polyethylene separator (having a porosity of about 48%) impregnatedwith a liquid electrolyte was disposed between a pair of the barelithium negative electrodes of Comparative Example 5, followed bysealing. Accordingly, a lithium symmetric cell having a Li/liquidelectrolyte/Li structure was prepared.

The liquid electrolyte was an electrolyte in which 1.0 M LiFSI wasdissolved in a mixed solvent of 1,2-dimethoxyethane (DME) to1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in aratio of 2:8 by volume.

The measurement results are shown in Table 2.

TABLE 2 Lithium ion transference number (T_(Li+)) Example 2 0.62~0.68Comparative Example 5 0.50~0.54

As shown in Table 2, although a protective film was additionallydisposed on lithium metal in the protected negative electrode of Example2, the protected negative electrode of Example 2 was found to have anincreased lithium ion transference number, as compared with the lithiumnegative electrode of Comparative Example 5.

Accordingly, a lithium battery including the protected negativeelectrode including the protective film of Example 2 has a decreasedinterfacial resistance and/or interface resistance, thereby improvingcycle characteristics of the lithium battery.

Without being limited by theory, it is believed that the increase in alithium ion transference number in the protective film of Example 2 maybe because the charge transfer of anions was suppressed and/or preventeddue to electrostatic attraction of the anions to the positively chargedparticle by the positively charged particle serving as a receptor ofanions, which relatively facilitated migration of lithium ions. Incontrast, in the lithium negative electrode of Comparative Example 5, itmay be difficult to suppress and/or prevent such charge transfer ofanions.

Evaluation Example 3: Measurement of Tensile Modulus of Protective Film

The protective film-forming composition prepared in Example 2 was caston a member, and THF in the resultant was gradually evaporated in anargon glove box for 24 hours at a temperature of about 25° C., andsubsequently, under vacuum at a temperature of 25° C., the result wasdried for 24 hours to prepare a protective film in the form of a film.The thickness of the protective film was about 50 μm.

The tensile modulus of the prepared protective film was measured usingDMA (DMA800, available from TA Instruments Inc.). The protective filmsamples for the tensile modulus measurement were prepared according tothe ASTM standard D412 (Type V specimens). The tensile modulus is alsoknown as Young's modulus.

Variations in strain with respect to stress (stress/strain) in theprotective film may be measured at a temperature of about 25° C., arelative humidity of about 30%, and a rate of 5 millimeters per minute(mm/min). The tensile modulus was calculated from the slope of astress-strain curve thereof.

As the result of tensile modulus measurement, the protective film ofExample 2 was found to have a tensile modulus of 10⁶ Pa or greater.

Accordingly, when the protective film of Example 2 is used, thevolumetric change of the lithium metal negative electrode and lithiumdendritic growth may be suppressed.

Evaluation Example 4: Evaluation of Thickness Change of Pouch Cell

Each of the lithium metal batteries manufactured in Examples 4 and 5 andComparative Examples 6 and 7 was charged with a constant current of 0.1C rate until a voltage of about 4.20 V (vs. Li), and maintained at aconstant voltage of 4.20 V (constant voltage mode) until a cutoffcurrent of 0.05 C rate. Subsequently, the batteries were discharged witha constant current of 0.1 C rate until the voltage reached 3.0 V (vs.Li) (Formation process, 1^(st) cycle).

Subsequently, each of the lithium metal batteries was charged with aconstant current of 0.2 C rate until a voltage of about 4.20 V (vs. Li),and maintained at a constant voltage of 4.20 V (constant voltage mode)until a cutoff current of 0.05 C rate. Subsequently, the batteries weredischarged with a constant current of 0.2 C rate until the voltagereached 3.0 V (vs. Li) (Formation process, 2^(st) cycle).

The batteries that went through the formation process were charged witha constant current of 0.5 C rate at room temperature (25° C.) until thevoltage reached 4.2 V (vs. lithium metal). Subsequently, the batterieswere discharged with a constant current of 0.5 C rate until the voltagereached a cut-off voltage of 3.0 V.

This charge/discharge process was performed repeatedly for 50 times fromthe 1^(st) cycle to the 50^(th) cycle of the charge/discharge process.

As the charging and discharging cycle was performed repeatedly, thechange in cell thickness upon charging and discharging was monitored.The partial results thereof are shown in Table 3. The change inthickness upon charging and discharging are indicated as thicknesschange after charging/thickness change after discharging.

TABLE 3 Thickness Thickness Thickness change upon 1^(st) change upon10^(th) change upon 50^(th) cycle of charging cycle of charging cycle ofcharging and discharging and discharging and discharging thicknessthickness thickness change after change after change after charging/charging/ charging/ thickness thickness thickness change after changeafter change after discharging discharging discharging (μm) (μm) (μm)Example 4 24/12 57/35 94/76 Comparative 24/24 77/48 119/98  Example 6Comparative 56/26 90/60 152/121 Example 7

As shown in Table 3, upon a charge/discharge process, the lithium metalbattery of Example 4 was found to have less change in thickness than thelithium metal negative electrodes of the lithium metal batteries ofComparative Example 6 and 7.

Without being limited by theory, it is believed that the decrease inthickness change of a lithium metal negative electrode may have resultedfrom the protective film of the lithium metal battery of Example 4including a positively charged particle, which may result in suppressionand/or prevention of charge transfer of anions in the vicinity of asurface of the lithium metal negative electrode. Thus, a side reactionbetween the lithium metal negative electrode and anions was prevented,consequently resulting in an increase in the lithium ion transferencenumber. In other words, without being limited by theory, an increase inthe concentration of lithium ions and uniform distribution of lithiumions at an interface between the lithium metal negative electrode andthe electrolyte increases the reversibility of the lithiumdeposition/dissolution reaction, thereby suppressing formation oflithium dendrites or increasing density of generated lithium dendrites.

In addition, upon a charge/discharge process, due to increasedreversibility of lithium deposition/stripping reactions, the amount ofconsumed lithium decreased, wherein the consumed lithium is not reducedback to lithium metal upon charging after being oxidized to lithium ionsupon discharging, thus resulting in the formation of lithium dendrites,or the like. Accordingly, the lifespan of the lithium metal battery mayfurther improve. For example, upon a charge/discharge process, thelithium metal negative electrode of Comparative Examples 6 and 7 isaccompanied by an increased volumetric change in the negative electrode,and this increased volumetric change in the negative electrode meansirreversible leakage of excess lithium contributing to the formation oflithium dendrites. Therefore, upon a long-term charging and dischargingof the lithium metal batteries of Comparative Examples 6 and 7, athickness of lithium metal may drastically decrease and be depleted,thereby shortening lifespan of the lithium metal batteries. In contrast,as the volumetric change of the lithium metal battery of Example 5 issuppressed, lifespan of the lithium metal battery may increase.

Evaluation Example 5: Evaluation of Pouch Cell Charging and DischargingCharacteristics

Each of the lithium metal batteries manufactured in Examples 4 and 5 andComparative Examples 6 and 7 was charged with a constant current of 0.1C rate until a voltage of about 4.20 V (vs. Li), and maintained at aconstant voltage of 4.20 V (constant voltage mode) until a cutoffcurrent of 0.05 C rate. Subsequently, the batteries were discharged witha constant current of 0.1 C rate until the voltage reached 3.0 V (vs.Li) (Formation process, 1^(st) cycle).

Subsequently, each of the lithium metal batteries was charged with aconstant current of 0.2 C rate until a voltage of about 4.20 V (vs. Li),and maintained at a constant voltage of 4.20 V (constant voltage mode)until a cutoff current of 0.05 C rate. Subsequently, the batteries weredischarged with a constant current of 0.2 C rate until the voltagereached 3.0 V (vs. Li) (Formation process, 2^(st) cycle).

The batteries that went through the formation process were charged witha constant current of 0.5 C rate at room temperature (25° C.) until thevoltage reached 4.2 V (vs. lithium metal). Subsequently, the batterieswere discharged with a constant current of 0.5 C rate until the voltagereached a cut-off voltage of 3.0 V.

This charge/discharge process was performed repeatedly and thischarge/discharge process was stopped at the cycle when the capacityretention reduced to 80%.

In other words, the number of cycles at which the battery had a capacityretention of 80% or higher was measured to evaluate lifespancharacteristics.

The capacity retention at an n^(th) cycle was calculated by Equation 1.The partial measurement results are shown in Table 4.

Capacity retention at the n ^(th) cycle(%)=(discharge capacity at the n^(th) cycle/discharge capacity at the 1^(st) cycle)×100%  Equation 1

TABLE 4 The number of cycles at which the battery had a capacityretention of 80% or higher Example 4 220 Comparative Example 6 180Comparative Example 7 130

As shown in Table 4, the lithium metal battery of Example 4 had anincreased number of cycles at which the battery had a capacity retentionof 80% or higher, as compared with the lithium metal batteries ofComparative Examples 6 and 7. Therefore, lifespan characteristics of thelithium metal battery were improved.

That is, in the lithium metal battery of Example 4, the migration ofanions was suppressed and/or prevented in the vicinity of a surface ofthe lithium metal negative electrode, and thus a side reaction betweenthe lithium metal negative electrode and anions was suppressed, ascompared with the lithium metal batteries of Comparative Examples 6 and7. Further, by an increased lithium ion transference number, volumetricchange of the lithium metal negative electrode and the formation oflithium dendrites were suppressed, thereby improving lifespancharacteristics.

As apparent from the foregoing description, according to an aspect, byemploying the composite electrolyte including a positively chargedparticle, a side reaction on a surface of a lithium metal negativeelectrode may be prevented so that the volumetric change of the lithiumbattery may be suppressed, thereby improving charging and dischargingcharacteristics of the lithium battery.

It should be understood that embodiments described herein should beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould be considered as available for other similar features or aspectsin other embodiments.

While one or more embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

1-34. (canceled)
 35. A composite electrolyte, comprising: a particlethat is positively charged by a coordinate bond with a cation; and alithium salt, wherein the particle comprises: a core comprising anorganic particle; and a functional group bound to the core via acovalent bond, wherein the functional group comprises a functional groupthat is bound to the cation by the coordinate bond, wherein an averageparticle size of the particle is about 10 nanometers to about 100micrometers, and wherein the functional group that is bound to thecation by the coordinate bond is represented by Formula 2:

wherein, in Formula 2, X is O, S, or a covalent bond, Z is N or B, R₅,and R₆ are each independently hydrogen, a C₁-C₂₀ alkyl group that isunsubstituted or substituted with a halogen, a C₂-C₂₀ alkenyl group thatis unsubstituted or substituted with a halogen, a C₂-C₂₀ alkynyl groupthat is unsubstituted or substituted with a halogen, a C₅-C₂₀ aryl groupthat is unsubstituted or substituted with a halogen, or a C₂-C₂₀heteroaryl group that is unsubstituted or substituted with a halogen,and R₇ is a C₁-C₂₀ alkylene group that is unsubstituted or substitutedwith a halogen.
 36. The composite electrolyte of claim 35, wherein amonomeric compound that provides the functional group that is bound tothe cation by the coordinate bond is a base, and wherein a pKa value ofa conjugate acid of the monomeric compound is 12 or less.
 37. Thecomposite electrolyte of claim 35, wherein the functional group that isbound to the cation by the coordinate bond is represented by one ofFormulae 11 to 18, or a combination thereof:


38. The composite electrolyte of claim 35, wherein the particlecomprises a polystyrene homopolymer, a copolymer comprising a styrenerepeating unit, a polymethyl (meth)acrylate, a copolymer comprising arepeating unit having a crosslinkable functional group, a crosslinkedpolymer thereof, or a combination thereof
 39. The composite electrolyteof claim 35, wherein the particle comprises a polystyrene homopolymer, apoly(styrene-divinylbenzene) copolymer, a poly(methylmethacrylate-divinylbenzene) copolymer, a poly(ethylmethacrylate-divinylbenzene) copolymer, a poly(pentylmethacrylate-divinylbenzene) copolymer, a poly(butylmethacrylate-divinylbenzene) copolymer, a poly(propylmethacrylate-divinylbenzene) copolymer, a poly(styrene-ethylenebutylene-styrene) copolymer, a poly(styrene-methyl methacrylate)copolymer, a poly(styrene-acrylonitrile) copolymer, apoly(styrene-vinylpyridine) copolymer, apoly(acrylonitrile-butadiene-styrene) copolymer, apoly(acrylonitrile-ethylene-propylene-styrene) copolymer, a poly(methylmethacrylate-acrylonitrile-butadiene-styrene) copolymer, a poly((C₁-C₉alkyl) methacrylate-butadiene-styrene) copolymer, a poly(styrene-(C₁-C₉alkyl) acrylate) copolymer, a poly(acrylonitrile-styrene-(C₁-C₉ alkyl)acrylate) copolymer, or a combination thereof, a crosslinked structurethereof, or a combination thereof.
 40. The composite electrolyte ofclaim 35, wherein the particle comprises a microsphere having an averagediameter of about 0.5 micrometer to about 50 micrometers.
 41. Thecomposite electrolyte of claim 35, wherein the lithium salt comprisesLiSCN, LiN(CN)₂, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, LiC(CF₃SO₂)₃,LiN(SO₂C₂F₅)₂, LiN(SO₂CF₃)₂, LiN(SO₂F)₂, LiSbF₆, LiPF₃(CF₂CF₃)₃,LiPF₃(CF₃)₃, LiB(C₂O₄)₂, or a combination thereof.
 42. The compositeelectrolyte of claim 35, further comprising a polymer.
 43. The compositeelectrolyte of claim 42, wherein the polymer comprises polyethyleneoxide, polyvinylidene fluoride, polyvinylidenefluoride-hexafluoropropylene, a poly(styrene-b-ethylene oxide) blockcopolymer, poly(styrene-butadiene), poly(styrene-isoprene-styrene), apoly(styrene-b-divinylbenzene) block copolymer, a poly(styrene-ethyleneoxide-styrene) block copolymer, or a combination thereof.
 44. Thecomposite electrolyte of claim 35, wherein a lithium ion mobility of thecomposite electrolyte is greater than a lithium ion mobility of acomparable composite electrolyte comprising the lithium salt and notcomprising the particle.
 45. A protective film, comprising the compositeelectrolyte of claim
 35. 46. The protective film of claim 45, furthercomprising a crosslinked product of a polymerizable oligomer locatedbetween the particles.
 47. The protective film of claim 46, wherein thepolymerizable oligomer comprises diethylene glycol diacrylate,triethylene glycol diacrylate, tetraethylene glycol diacrylate,polyethylene glycol diacrylate, dipropylene glycol diacrylate,tripropylene glycol diacrylate, ethoxylated trimethylolpropanetriacrylate, acrylate-functionalized ethylene oxide, 1,6-hexanedioldiacrylate, ethoxylated neopentyl glycol diacrylate, propoxylatedneopentyl glycol diacrylate, allyl methacrylate, trimethylol propanetriacrylate, trimethylol propane trimethacrylate, pentaerythritoltriacrylate, ethoxylated/propoxylated trimethylolpropane triacrylate,glyceryl propoxylated triacrylate, tris(2-hydroxyethyl) isocyanuratetriacrylate, pentaerythritol tetraacrylate, dipentaerythritolpentaacrylate, or a combination thereof.
 48. The protective film ofclaim 46 further comprising a liquid electrolyte comprising a lithiumsalt and an organic solvent.
 49. The protective film of claim 48,wherein the organic solvent comprises ethylene carbonate, propylenecarbonate, dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, fluoroethylene carbonate, γ-butyrolactone, dimethoxyethane,diethoxyethane, diethylene glycol dimethyl ether, triethylene glycoldimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycoldimethyl ether, succinonitrile, sulfolane, dimethyl sulfone, ethylmethyl sulfone, diethyl sulfone, adiponitrile, tetraethylene glycoldimethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether, or a combination thereof.
 50. The protective film of claim 45,further comprising an ionic liquid, a metal salt comprising a Group 1element of the Periodic Table of Elements, a metal salt comprising aGroup 2 element of the Periodic Table of Elements, a nitrogen-containingadditive, boron nitride, an ion conductive polymer, or a combinationthereof.
 51. A lithium battery comprising: a positive electrode; aprotected negative electrode comprising lithium metal or a lithium metalalloy, and a protective film on the lithium metal or a lithium metalalloy; and an electrolyte located between the positive electrode and theprotected negative electrode, wherein the protective film comprises acomposite electrolyte comprising: a positively charged particle, aparticle that is positively charged by having a coordinate bond with acation, or a combination thereof; and a lithium salt.
 52. The lithiumbattery of claim 51, wherein the electrolyte comprises a liquidelectrolyte, a solid electrolyte, a gel electrolyte, a polymer ionicliquid, a separator, or a combination thereof.
 53. The lithium batteryof claim 51, further comprising: a monolayer structure comprising afirst liquid electrolyte layer in contact with the protective film ofthe protected negative electrode, or a monolayer structure comprising afirst liquid electrolyte layer comprising a separator in contact withthe protective film of the protected negative electrode, wherein a firstliquid electrolyte is impregnated in the separator.
 54. The lithiumbattery of claim 51, further comprising a multi-layer structurecomprising: a first liquid electrolyte layer comprising; a separator incontact with the protective film of the protected negative electrode,wherein a first liquid electrolyte is impregnated in the separator; asecond solid electrolyte layer in contact with the first liquidelectrolyte layer and comprising a ceramic conductor; and a secondliquid electrolyte layer in contact with the second solid electrolytelayer, or a multi-layer structure comprising: a first solid electrolytelayer in contact with the protective film of the protected negativeelectrode and comprising the composite electrolyte; a second solidelectrolyte layer in contact with the first solid electrolyte layer andcomprising a ceramic conductor; and a second liquid electrolyte layer incontact with the second solid electrolyte layer, or a multi-layerstructure comprising: a first solid electrolyte layer in contact withthe protective film of the protected negative electrode and comprisingthe composite electrolyte; a first liquid electrolyte comprising aseparator in contact with the first solid electrolyte, wherein a firstliquid electrolyte is impregnated in the separator; a second solidelectrolyte layer in contact with the first liquid electrolyte layer andcomprising a ceramic conductor; and a second liquid electrolyte layer incontact with the second solid electrolyte layer.